Redesigned directory pages (WIP)

This is an initial conversion of the directory pages from the old style
to the new style which is based on Twitter Bootstrap.

Still some remaining work to be done. You can see a screenshot here:

http://i.imgur.com/MPEngGx.png
Merge remote-tracking branch 'tarcieri/redesigned-directory-page' into merged

Conflicts:
	src/allmydata/web/directory.py