IntermediateSerializer now properly reads nullable types which have a non-null value.
ElementSerializer<T> now properly deserializes char type properties, including values that would normally be considered delimiters.
Non-public content processors are now exposed to the PipelineProject and to MGCB (this matches XNA behavior).
Merge pull request #3078 from SickheadGames/MergeImportedProject

Minor IntermediateSerializer fixes.