TLDR: artifacts are going to move around in Binaries\Debug and the directory is going to get a lot bigger.

At a high level build projects can be classified into three categories based on how they write output:

- incorrect: a given output path is written to more than once with different contents
- less correct: a given output path is written to more than once but always with the same content
- correct: a given output path is written to exactly once

Today the roslyn build is decidedly “incorrect” as pretty much every file is written directly into Binaries\Debug. This means it ends up writing pretty much every Visual Studio SDK DLL twice: once for Dev14 and once for Dev15. For example at various points in the build Binaries\Debug\Microsoft.VisualStudio.Text.Data.dll may refer to Dev14 and at others it’s Dev15. If this seems like a scary proposition for a build that’s because it is indeed scary and it has real consequences. By now pretty much everyone on the team has hit the build race condition that is dragging down our PRs.

The general fix here is to move build outputs into separate directories. Instead of building to $(Configuration) projects now build into say $(Configuration)\Exes\$(MSBuildProjectFileName). This will have a substantial increase in the size of Binaries. We will be looking into ways to reduce that. In the short term though build stability far outweighs the size increase.

This change takes us most of the way to "correct". There are several places I had to compromise in order to get this initial change in:

- UnitTests still build to a common output folder (one for Dev14, another for Dev15). Pulling unit tests apart is going to take a bit of work.
- Every project has a <RoslynProjectType> entry. This will go away in the future for most projects. It's temporarily needed so I can fix roslyn-internal in parallel without taking down the build.
- VSL.Imports.targets is messy. Unavoidable for now due to the above. It will get cleaner as I iterate on this.

None of these are relevant to the underlying race condition. Hence it's okay to push them off.

diagnostic and codefix.

The ImportGroup element is just noise.  It was also used very inconsistently in the repo and often within the same project file.  Just remove it.

.. to move or to rename to.

In case of nested types, the accepted style of naming the file is either
by the standalone typename or with a dotted name derived from its type
hierarchy. For e.g: If type B is nested inside type A, acceptable file
names for type B is B.cs or A.B.cs

Offer these as suggested filenames if the file is named something other
than either of these two. These suggestions are then picked up and
surfaced as "Move to.." or "Rename file to.. " code actions.

The dependency projects serve a few purposes:

- Help ensure package unity by serving as a single place for a NuGet reference.
- Make NuGet updates simple by having a single place to change.
- Grouping together related packages to make it easy to take a dependency on say Visual Studio editor.

The first two points are largely obsolete now that our project.json references are strictly validated on every build and have a single update mechanism.  This meant a lot of our depnedency projects were just making Roslyn.sln bigger.

As such I went through and deleted all of them which had only 1 or 2 project.json entries.  I left the VS ones which tend to group 10+ references together.  They are still serving a valid "reference VS" purpose.

.. Move type tests.

Tests for following code actions in C# and VB:
1. Move type to new file
2. Rename type to match filename
3. Rename file to match typename

AbstractMoveTypeTestsBase implements shared helpers for testing MoveType
Refactoring.

CSharpMoveTypeTestsBase and BasicMoveTypeTestsBase contain language
specific test helpers.

Tests are organized as MoveTypeTests.<CodeAction>.cs/vb

where code actions are
Move type to new file
Rename type to match filename
Rename file to match typename etc.

The feature code is mostly language agnostic, so it suffices if we pick
one language and test it heavily and make sure simple things and
language specific parts work as expected, on the other language.

Issue #11841 found that, due to a MEF bug, the Features assemblies could not properly be included in a MEF composition. This was worked around by combining [ExtensionOrder] attributes where multiple attributes had been specified. This change adds a tests for C# and VB to ensure that a CompletionService can be acquired from an AdhocWorkspace that is created with MefHostServices that include the Features assemblies.

I verified that these tests fail without the workaound described above, and pass with the workaround in place.

* initial port from CSharpEssentials

* responding to feedback.
removing syntax rewriter and incorporating formatting rules into formatter

* responding to cryus' feedback

- general logic cleanup
- moving methods to abstract base class

* initial port from CSharpEssentials

* responding to feedback.
removing syntax rewriter and incorporating formatting rules into formatter

* responding to cryus' feedback

- general logic cleanup
- moving methods to abstract base class

1. Reference a bunch of stuff from Nuget packages instead of VS.
2. Move to Update 2 versions of packages.
3. Now that we are using the packages, we're referencing
   Microsoft.VisualStudio.Shell.14.dll instead of .15 again.  This means
   that types that moved to Shell.Immutable.15 are not type forwarders.
   Luckily we didn't need anything from Shell.Immutable.15 in the project
   where it was a problem.

1. Split out the tests into ones with built-in IDE analyzers and ones with only third party analyzers
2. Tests depends on closed side changes (add/update VS tao actions)

This brought along some references to Microsoft.VisualStudio.Threading
that we previously didn't have. Nothing was wrong with this, but it
meant I had to fix some namespace qualifications that were assuming the
"Threading" namespace was unambiguous.

Rewrite PopulateSwitch diagnostic and fixes.  Fix bug in generator that causes crashes when generating a default case for VB.NET switches.

This allows us to build with Update 2 installed, where the version number
is different.

This allows us to build with Update 2 installed, where the version number
is different.