Changes BuildBoss to enforce portable test projects use the
UnitTestPortable label. Probably going to remove that in the near future
but at this point it's still required.

Use multi-targeting to expose compilation primitives

Merged on behalf of @brianhartung. Thanks!

Merging on behalf of @megafinz. Thanks

Use explicit casts rather than `as`

Rewrite CryptoBlobParser to use BlobReader/BlobWriter instead of casts

Fixes #20693

Add user facing option to place blank lines between using/import groups.

Merge dev15.3.x to master

# Conflicts:
#	src/EditorFeatures/TestUtilities/Remote/WatsonReporter.cs
#	src/EditorFeatures/TestUtilities/ServicesTestUtilities.csproj
#	src/VisualStudio/Core/Next/Remote/JsonRpcClient.cs
#	src/Workspaces/CSharp/Portable/CSharpWorkspace.csproj
#	src/Workspaces/Core/Portable/Workspaces.csproj
#	src/Workspaces/VisualBasic/Portable/BasicWorkspace.vbproj

Lambda analysis uses a lot of pooled data structures (as it should,
since it will be redone from scratch using the exact same structure for
every method) but did not properly free everything. This should properly
recursively free all pooled data structures used in analysis.

Correct badge icon URLs to reflect renamed builds in DotNet's Jenkins CI

Portable unit tests now build their desktop variants directly to the
UnitTests directory in a runnable state. This allwos tests to be run
directly and removes the need for the desktop deployment project.

Remove additional esent references.

The error operations need to distinguish between adding errors to the
known list and printing them out to the console. This avoids an
exception foreaching over the error list at the end of the script
(previously it was adding them while iterating).

This changes our core Roslyn.Test.Utilities project to use
multi-targeting to control how we create our core compilation helper.
Previously this was done by having a separate runtime specific assembly
which was probed at runtime.

The intent of this change is to make our build more correct here. I can
now target just Roslyn.Test.Utilties with a net46 framework and get a
runnable asset out of it. This is necessary in order for our unit tests
to successfully run when moved to multi-target.

Presently this makes it multi-target across net46, netcoreapp2.0 and
netstandard1.3. The impl in netstandard 1.3 simply throw for this
specific API. Over the long term it make make sense to pull this out to
a separate library that only targets net46 + netcoreapp2.0. That
requires a much deeper investment in multi-targeting though. Decided to
start smaller for now.

By default Invoke-WebRequest will fail if IE hasn't gone through first
configuration setup on the machine. Parts of our infrastructure don't
run IE and as a result our uses of Invoke-WebRequest were failing. Fixed
by passing the UseBasicParsing switch.

Recent builds of the SDK introduced a bug around referencing netstandard
1.6 projects. This trigged on several Roslyn projects and cause build
breaks with newer builds of VS.

Suppressing the check for now. Will undo when we move to 2.0 SDK

https://github.com/dotnet/roslyn/issues/21183

Fix a couple of infrastructure issues

Fix a couple of infrastructure issues

replaced crash to NFW. it will now show info bar and throw cancellati…

Remove Esent entirely from Roslyn.

By default Invoke-WebRequest will fail if IE hasn't gone through first
configuration setup on the machine. Parts of our infrastructure don't
run IE and as a result our uses of Invoke-WebRequest were failing. Fixed
by passing the UseBasicParsing switch.