Removed redudant supertypes.
Fixed TryGetValue().
MGCB links against MonoGame now and not MS XNA.
ContentCompiler.Compile() is now internal.
Fixed WriteXnb to use ContentCompiler directly.
Removed the MSBuild tasks from the pipeline project.
We now throw PipelineException when we cannot find or execute importers or processors.
We now print errors to the console in ContentProject.Build().