Remove margins on navigator list
Fix tab title width
Add jstree dependency
Get ready to ditch awful jstree library.

Wasted a good portion of the day trying to get jstree to work adequately but
ran into an endless stream of problems.  The API is poorly thought out,
inconsistent, and un-/mis- documented.  create_node and get_node return
true/false instead of sane values, and there's no error logging whatsoever
(functions silently fail).  Note to future self: avoid jstree like the plague.
Good riddance to jstree