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