Remove placeholder objects for subfolders

A subfolder in a container is now represented solely by the prefix of
an object name delimited by a forward-slash (/). If an object exists
in a container that matches the implied subfolder of another object,
each will be displayed in the objects table.

Implements bp swift-folder-prefix

Change-Id: I05252c1db34fdf6584a71e8827ff6f8363bf0488
Replaces ugettext with ugettext_lazy in the dashboard-related files

While most files correctly import ugettext_lazy, some are importing ugettext instead.
This is causing some parts of the dashboard to not translate correctly when a user
switches languages. The core cause of this is because ugettext will translate the
string once when the django application starts. ugettext_lazy will translate when the
string is retrieved.

Change-Id: Ibbdef60b3616d13aa7c2c5449ca592bf214a5f71
Fixes: bug #1124276
Merge "Remove placeholder objects for subfolders"
Improved security group rule editing.

Splits rule editing and rule creation out so that
rather than being on one modal form (which is dismissed
after taking any action on the rules) they are instead
contained in their own security group detail view, with
create/delete as their own discrete forms/actions which
return to that same view.

This also reworks the form to be more explicit and
user-friendly in terms of the various options provided,
making it more responsive, and making it better documented.

Incidentally fixes some problems in the documentation.

Implements blueprint security-group-rules.

Change-Id: I866dd4fe0c74148140422aab9172be4f496689a9