Extend our own intermediate view parent class

That way if we want to add utility to all of our views it
will be easy to do.
Refs #136. Move alerts to upper right, and improve styling
Have server generate index html

That way, it has the ability to dynamically change which
plugin static code gets imported into the front-end app, without
the client-side build process having to know which plugins are
enabled at build time.
Style improvements on hierarchy widget and item view
Add folder update action, and UI for it in web client
Indicate beta API version status
Add grunt build targets for web client content in plugins
Add frontend event hooks for before and after app is loaded
Add built templates from plugins into built JS
Use grunt-contrib-jade to build jade in the same way as css/js

This technology did not exist when we first started using jade. I've
also upgraded our jade runtime version from a beta version to the
latest official release :)
Add some docs for frontend plugin development
Merge pull request #147 from girder/frontend-plugins

Frontend plugins