Basic tests for the update_generated_fields command.
Updated the update_generate_fields command.

Dropped the reset_slugs part (that could potentially be dangerous
and only proved to be useful once or twice).

Designed a method to mark classes as needing a resave after adding
new languages -- you should add a "generated_fields" attribute to
your classes that have translatable fields that get automatic values
on model save.
Renamed update_generated_fields command to resavemodels.