Support Hours/Minutes/Seconds intervall in update_modules()

[anderspetersson]

Currently, the update_module()-function will update the given days stats if called multiple times per day. This should be configurable on the module level so that if interval on a module is set to minutes it should create a new entry in the database instead of updating the old one.

[anderspetersson]

When Django 1.6 is out, this should be easy to do using the new __hour, __minute and __second lookups in the ORM. https://docs.djangoproject.com/en/dev/ref/models/querysets/#std:fieldlookup-hour