Fix for GitHub issue 632:
We now have a ModelBuilder and a BasicModelBuilder. The ModelBuilder has conventions which update the model but the model code generator uses BasicModelBuilder and does not generate anything for ValueGenerationOnSave and ValueGenerationOnAdd. When the snapshot is created these will have default values instead of the correct values. The fix generates code for the property value generation settings.
Use ContextTypeAttribute during migration discovery
Merge branch 'release' into dev
I really hope all this negativity is short lived... (Update value generators to be able to mark generated values as temporary)

This change allows value generators to mark generated values as temporary, which in turn will allow the update pipeline to make a decision as to whether a store-generated value is expected.