Fix for broken 'Select All' functionality

Previously broken due to different HTML elements than expected by ``actions.js``. Fix includes pulling in the latest ``actions.js`` from Django 1.7

I tried to find a way to conditionally use ``actions.js`` only on older Django versions to prevent it from becoming stale over time, but had no luck since it is a static file.

Risk of it becoming stale is rather low, though. It has only had ~6 changes in the last 4 years, and hasn't been touched in nearly a year.