Redid a bit of CSS on the compose box
Added _nice_name Jinja extension to trim unruly from as per #648
Added the .contains javascript global String function
Added default 'density' CSS class to sidebar & search results
Commented out Compose autosave, as I've been working to refine it more... it wasn't ready for prime time, sorry dudes & dude-ettes :/
 Enhanced plugin loading for external plugins.

 New manifest.json features are:
 - startup and shutdown hooks
 - register mailboxes
 - pass config to mailbox parse_path

 Necessary enhancements for external LEAP plugin.