Improvements in csv export for usage data

Added a csv writer using the 'csv' library to format
properly exported data - escaping, encoding etc.
Added a HttpResponse-based class to handle csv generation
Added translation for the CSV columns and template.

Fix bug #1158383

Renamed few occurencies of 'tenant' to 'project'.

Also added a new 'project' in nova_data.py, which required
some refactoring of few tests, that didn't consider the current project
for project-based calls.

Note: I've added a StreamingHttpResponse example,
which is introduced in Django 1.5+ and being advised in the ticket.
However, my opinion is that at the moment we don't need this - it is
too complicated for the current usage.

Change-Id: I18bd70a23b7b8389c7c0f96dbf8794fea5e1e75b
Revised a few confusing quota legends on the overview page.

Change-Id: I21babc484168de2501086c3f542bccb14b0a974a
Fixes: bug #1194966
Always load CSS files first

Loading Javascript externals is usually blocking
the browser from processing the file further. Move
CSS file loading to front so that they can happen
in parallel.

Change-Id: I301b3df62269528306b45c947fef49a5fa8dbfeb
Merge "Improvements in csv export for usage data"
Merge "Revised a few confusing quota legends on the overview page."
Merge "Always load CSS files first"