Handle IDs better for pictures, senses
Handle IDs better for pictures, senses

Pictures will persist their GUID, and senses their SenseId. Note the
comment in the code about "This doesn't quite feel right": I'll need to
revisit this line once I start round-tripping data, because that's when
I'll likely discover what's the *correct* way to round-trip sense IDs.

ermshiperete/LfMerge,ermshiperete/LfMerge,sillsdev/LfMerge,sillsdev/LfMerge,ermshiperete/LfMerge,sillsdev/LfMerge