added two new settings - COMPRESS_ROOT and COMPRESS_URL which point by default to MEDIA_ROOT and MEDIA_URL respectively. That settings make ability to use both django 1.3 django.contrib.staticfiles and django-compress without incompatible issues

Signed-off-by: Timothée Peignier <timothee.peignier@tryphon.org>

rely on the fact that compressed filenames always increase. os.listdir returns filenames in arbitrary order, so they must be sorted (in reverse order) to get the most recent

rely on the fact that compressed filenames always increase. os.listdir returns filenames in arbitrary order, so they must be sorted (in reverse order) to get the most recent