Upgrades System.Collections.Immutable to 1.1.34-rc and
System.Reflection.Metadata to 1.0.19-rc.

This reverts commit b37052d0.

The code base no longer uses StyleCop.  Removing lingering references to
it from the code base.

This changes our projects to consume xUnit through NuGet instead of our checked in binaries in Closed\Tools\xUnit.  This is another step in removing project scrubber.  (changeset 1396548)

This changeset introduces the concept of a "global" nuget package. The references to the NuGet packages are inserted into the Open VSL.Settings.targets file, which is imported into every project in Roslyn. This ensures that every project automatically gets these "global" packages. (changeset 1386548)

Updates System.Collections.Immutable and System.Metadata.Reader to versions 1.1.33-beta and 1.0.18-beta, respectively.
     Updates VSMEF to the latest build from VSPRO_1.

     A few code fixes:
     - ImmutableArrayInterop is gone
       - in product we used in a couple of places where we now just create a copy of the byte[] (MetadataWriter)
       - test infrastructure uses a workaround with explicitly laid out union to avoid copies of large metadata blobs
     - EditorTestApp class was incorrectly importing MEF components resulting in a cycle. The new VSMEF reports such errors. (changeset 1385613)

***NO_CI***
 (changeset 1357023)

This also updates Microsoft.Net.ToolsetCompiler to the corresponding version. (changeset 1355122)

***NO_CI***
 (changeset 1341082)

Update the version of the toolset compilers used for build and make sure that all projects are using the toolset NuGet. (changeset 1330804)

Moving the samples we ship with our SDK to open source.  Also including the interns analyzers, code fixes, and tests. (changeset 1314543)

for now, it only contains Formatting Tests, but in future, we should split mixed lang tests in service test to each own one. (changeset 1223390)

Update the Roslyn Toolset to a version with an official, signed, NuGet package.

The new package is Microsoft.Net.ToolsetCompilers.0.7.4032713-beta.nupkg. (changeset 1217415)

The new package is Microsoft.Net.ToolsetCompilers.0.7.4032713-beta.nupkg. (changeset 1217346)

Update System.Collections.Immutable 1.1.18 -> 1.1.20
Update System.Reflection.Metadata 1.0.8 -> 1.0.9 (changeset 1211547)

Removing duplicate entries from repositories.config (changeset 1211406)

Update System.Reflection.Metadata 1.0.8 -> 1.0.9 (changeset 1211431)