[1.3.X] Tidy up the sessions documentation creating links for session methods...

[1.3.X] Tidy up the sessions documentation creating links for session methods and crosslinking settings

Backport of r16245 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.3.X@16246 bcc190cf-cafb-0310-a4f2-bffc1f526a37