Hierarchy widget.
JS style fixes
Collection model and REST endpoints
Upload and assetstore framework

This huge commit creates an initial assetstore framework and adds
chunked upload support and an HTML5 client uploader. Further
implementation of the assetstore model will be added in future
commits. The first assetstore type implemented partially here is
the filesystem assetstore, which simply stores files on the
filesystem.
When upload finishes successfully, refresh view and dismiss modal
Support adding files to upload with drag and drop.

Also use prettier (non-native) browse for files button.
Gracefully handle item name collision.

Append (n) to the end of the name until it is unique, and carry on.
Implement filesystem assetstore storage
Add upload resume capabilities.
Finish the accessors in assetstore_utilities

* Also add method to assetstore adapter for getting capacity info
* Started implementation on the assetstore model itself
Client-side router implementation
Added a simple jquery plugin as a utility for cleanly creating
modal views without duplicating event bindings.
Frontend cleanups; added prototype admin console
Prototype views for creating new assetstores.
Implement assetstore creation
Require absolute path for assetstore root dir
Show assetstore capacity using jqplot

This also has the benefit of adding jqplot to the project, which
will be generally useful.
Implement download with filesystem assetstore adapter
Support offset when downloading a file
New policy: first user created will be set as site admin

Also fixed a bunch of failing tests, and added a plugin mgmt link
on the admin console.