Don't try to import mt_settings unless we know that USE_MODELTRANSLATION is true.
Registration test doesn't need skipping with USE_I18N true.
Better setUpClass for the content translation test case.
Auto population (setting) test.
Use settings prepared in setUpClass in the derived fields processing tests.
Made a section for internationalization settings.
Dropped the optional apps in testing change.

(This has been decided on the pull #1168.)
Merged master (by rebasing and squash-merging the non-dev branch).

The changes included seperating short_url generation that allowed to clean
things a bit on the derived fields processing commit.
Fixed squash-merging settings proliferetion.
Fixed switched skip comments.
Allowed modeltranslation to be inserted into installed, not optional apps.
Process internationalization settings before re-tupling settings.
Modeltranslation needs to be before django.contrib.admin in INSTALLED_APPS.
Ignore the registration test complain about Settings for now.

Placeholder for settings translation.