Comment "regarding" field not round-tripping correctly

[rmunn]

Once I start working on #339, I may want to create a test for this scenario. Repro:

• Start with sena-3 project.
• Language Forge creates comment on word "adidi", Portugese gloss "bom"
• LF S/R
• Delete LF project
• Clone from LexBox
• Click on "adidi"
• The comment is there, but the UI indicator next to the field has been lost

This is because the "regarding" field isn't getting set correctly on the LF side of things, for reasons yet to be determined.

[rmunn]

The TODO status on comments is also failing to round-trip, due (in part) to the model differences between FLEx and Language Forge (FLEx doesn't have TODO). There's code that's supposed to round-trip it, but it might be failing.