Interim work on audio import and processing.
Merge branch 'develop3d' of https://github.com/mono/MonoGame into pipeline
Added content building classes.
Added solution for windows content pipeline.
Added project for the MonoGame Content Builder command line tool.
First pass at parsing the .contentproj and executing the build.
WIP for pipeline.
* Added XML documentation to several classes.
Merge branch 'develop3d' of https://github.com/mono/MonoGame into pipeline
We better handle exceptions in content processing.
PipelineManager expects absolute assembly paths now.
We now use the XNAGSv4 environment variable to resolve XNA assemblies.
We now try to load assemblies from the GAC if possible.
The output folder name is now specified on the command line.
Merge branch 'develop3d' of https://github.com/mono/MonoGame into pipeline
Merge branch 'develop3d' into pipeline
Merge branch 'mgcb' of https://github.com/SickheadGames/MonoGame into pipeline
Merge branch 'develop3d' of https://github.com/mono/MonoGame into pipeline
First XNB file has been written
Most of the SongProcessor has been implemented.
PipelineManager now checks its own assembly by default, including non-public types (a lot of built-in types aren't public).  External assemblies still only use public types.
Merge branch 'develop3d' of https://github.com/mono/MonoGame into pipeline
Merge pull request #1203 from slygamer/pipeline

[Pipeline] First XNB file has been written