Update yank plugin
Allow plugins to do non-destructive key binds
Hookup bind command

Need to make string completions display their text.

Anyway, no validation is done of the key or the command. The worst case
scenario is that you bind to gibberish that's never called or you mess
up a command and get an error on use.
Minor key fixes
Add pre and post hooks for plugin format stuff

These format strings are way out of hand and the story refresh/render
needs to be simplified greatly, however this should allow plugins to
easily bracket the main content (i.e. title or tag).