UI improvements when deleting objects.

Shows nested child objects that will be deleted when deleting a single object or multiple objects.

Includes some hacky tests for NestedObjects in the example app.
Use utils.model_options().
Use utils.model_options() in views and change utils import.
Tweak NestedObjects (and tests) comments.
PEP-8 work
New immutable object type that is properly frozen. Part of #155
New immutable object type that is properly frozen. Part of #155
fixes #155, which is moving models.py to types.py. Using admins.py as an alias for the old models.py module
 #101 #103 added change password, logout views
use django-braces for login required views
login view
merge from develop
change password form dependent from user
deleted LoginRequiredMixin
added tests
fixed names
revert auth tests
Merge pull request #146 from d1ffuz0r/issue_101

 #101 #103 added change password, login, logout views
Added Roman Gladkov as a contributor, PEP8 and djadmin2 standards fixes
replace django.contrib.admin introduced in last pull request with our own native form