UI tweaks

refs #5260

Added messages for displaying confirmation messages.  Change post-create
redirects.  Added more info to spaces list page.
Delete AIP from filesystem when delete request approved

refs #5250

Delete AIP from locally mounted or ssh-only access filesystems when
delete request approved.  Display success and error messages to user
when done.
Code cleanup

refs #5479

Fixed bug where two subsequent delete requests would get through, since
the store_data was different.

Removed django.utils.simplejson in favor of json. Replaced len(queryset)
with queryset.count()