First stab at list indent/outdent

Authored by Catrope.


First stab at list indent/outdent

This works pretty well, the only problems I found are:

  • when selecting multiple list items, only the first is in/outdented
  • there's no special handling for child lists, so the behavior for in/outdenting list items that have a child list can look weird, but it's consistent

Also needs more documentation

Change-Id: I6f4f3725e57a590196d7d638a77b87ea85586dc8