review objtype / flavor usage

[sbailey]

Our usage of flavor and objtypes is getting a little out of hand in desispec. ELG, LRG, QSO seemed straightforward enough, but we are starting to get things like MWS vs. MWS_STAR, STD vs. STD_FSTAR vs. FSTD, etc. This issue is a placeholder to think about the big picture of how this should work and do some cleanup.

[moustakas]

With data now in-hand, I think our choices are basically now baked in. Closing with no action.