No longer minify CSS when generating from LESS

This can be done by django-compressor (or similar) during deployment.
Tweak basket form error message

No need to include product title when the error is displayed within the
basket line form.
Set a default max size for a basket to avoid database errors

Without this, a silly quantity of 9999999... can cause database
integrity errors when submitted via the basket form.  We set a sensible
maximum value to prevent this.

Fixes #278
Upgrade fallback jQuery to 1.7.2

Had fallen out of sync with the Google CDN one that gets loaded by
default.  Only noticed while trying to hack on the tube!