Fix error in username_available.json api docs, show the whole parameter instead of the first letter
Translate and fix text on compact buttons
Add some info and link to wiki in formatting help
Skip loading plugins that fail to import unless specified.
Add a basic event hook system for plugins to use.

This allows decoupled registration of interest for plugins.
plugins: Ensure load_controllers is called in paster shell/run as well.

load_controllers is the safe place to do imports of things that rely on
`g` et al being in the correct state. It was not being called in paster
shell or run which meant that any hooks defined in a module that relies
on `g` at module scope (e.g. things importing model or controller code)
would not be connected in those contexts.
Thing: Use a hook for on_thing_commit.
Add some request-related global hooks.
js_config: Add a hook for mutating js_config.
Add hook for Comment._gild().
Add comment.new hook.
Add hook to Printable.add_props.
Plugins: make on_load take "g" so it can add stuff to globals.
Allow g.cache_chains to be extended after creation.

Cache chains added in plugins need to be reset, too!
Add extra_stylesheets knob to Reddit.

This provides an easy way for plugins to add extra separate stylesheets
to the site.
Add Backbone 0.9.10 to the main JS.
Add util for locating static files. Move to static.py.
Search static directories in a consistent order.
Whitespace.
Clean up file reading in js.py.