Added PipelineBuildEvent.Extension.
Added "Cleaning" log message.
Add error if the source file does not exist.
Fix a runtime error when getting GraphicsCapabilites in Linux
We now write a log of all the source files processed.
We can now properly clean files that have been removed from the previous build.
Added /incremental flag to disabling cleaning of previous files.
We now remove duplicate input source files.
Added SourceFileCollection.cs to MGCB for Linux and Mac.
Fixed debug config in Linux and Mac csproj.
Added target /platform, /profile, and /config options to MGCB.
Merge pull request #1257 from SickheadGames/mgcb2

Even More MGCB Improvements
Merge remote-tracking branch 'upstream/develop3d' into develop3d
Merge pull request #1255 from dellis1972/develop3d

Fix a runtime error when getting GraphicsCapabilites in Linux
Merge branch 'develop3d' of https://github.com/mono/MonoGame into develop3d
Merge branch 'develop3d' of https://github.com/azchohfi/MonoGame into develop3d