Draft: Manager can link properties

See #64

Essentially, this allows one to tie together configurable subsets of managed keys. If the table contains, for instance, preview\..*\.index, then whenever any preview index is changed, all preview indices are set to this new value. Or if it's preview\.(raw|rawGain)\.index and preview\.(corrected|gainMap)\.index, each pair is handled separately. No overlap between groups, please.

I think that's a neat solution, but it is of course another thing to configure - and super confusing if you don't know what's going on.

Bonus confusibility: what about standalone modules?