Implement proper permission checkin in Admin2

Uses Django's builtin per-model permissions (add/change/delete plus view which we'll add)
and also supports per-object permissions.
Create view permissions for all models when syncdb is run

Works exactly the same way as that of the standard add/change/delete permissions
(the code is in fact copied from there).
Merge remote-tracking branch 'upstream/master' into permissions

Conflicts:
	djadmin2/models.py
Merge remote-tracking branch 'upstream/master' into permissions
Merge pull request #54 from ludw/master

runtests.py did not include #!
Integrate permissions into views

Views now ensure that the user has corresponding permissions.
Also, action buttons, e.g. Add, are shown only when the user can actually do that.
Merge remote-tracking branch 'upstream/master' into permissions

Some cleanup as well.
Display model name in template
Merge pull request #59 from audreyr/list-view-model-name

Display model name in template
Merge
Update CONTRIBUTORS.txt
Document fixing
Partial checkin of #61
remove confusing comments
Merge remote-tracking branch 'upstream/master'
Add tests to core
Index work
Merge branch 'admin-core-tests' of git://github.com/inglesp/django-admin2 into inglesp-admin-core-tests
Merge remote-tracking branch 'upstream/master'