feat(attributes): Add backfill button in flat and classbased allocation modes

Partial implementation of a "distribute points now" button for backfilling accrued Attribute points. Works with flat and classbased allocation so far; taskbased will require much fancier handling.
fix(allocateNow): Send empty object to user.ops per @colegleason suggestion

Tested with both implemented allocation modes, looks good!
Merge remote-tracking branch 'upstream/sabe/attributes' into develop