Ignore pivot channels in animations.
Update MonoGame to support service dependencies
Fixed Song.PlayPosition that is invalid on Android after a Play-Pause cycle
Merge commit '495761c' into ModelBacklog
Fixed bad keyframe continuity.
XNA appears to default this to null, not string.Empty
More model refinements.

(Cherry picked minus duplicated effort in ModelProcessor)
Merge pull request #3075 from SickheadGames/ModelBacklog

Misc model pipeline fixes
Merge pull request #3074 from SongArc/feature/android_playpause_fix

Fixed Song.PlayPosition on Android
Reduce allocations in GraphicsDevice.PlatformApplyRenderTargets()
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.
Merge pull request #3077 from flyingdevelopmentstudio/FixOpenGLGraphicsDeviceGarbage

Reduce allocations in GraphicsDevice.PlatformApplyRenderTargets()
Fixed another case IntermediateSerializer for correctly handling char type deserialization.
FontDescription and related types (CharacterRegion) are now compatible with the IntermediateSerializer according to XNA specifications.
FontDescriptionImporter now uses IntermediateSerializer rather than directly parsing xml, this matches XNA behavior. This allows derived FontDescription types to be deserialized and processed in a custom processor while reusing the stock FontDescriptionImporter.
Adding unit test which uses IntermediateSerializer to deserialize a child type of FontDescription.
Merge pull request #3012 from hach-que/protobuild-services

Update MonoGame to support service dependencies
Merge pull request #3079 from SickheadGames/MergeImportedProject

FontDescription / IntermediateSerializer compatibility
Fixed implicit operator.