Remove paper_trail

[orenyk]

Our logging functionality (see #319) isn't really set up for production. Currently, it's broken on BMEC since it loads all of the log items at once; this is similar to the issue with the reservations index view (see #708). Considering that some of the views are also broken (see #689) and I don't think anyone's using it, on top of the fact that the equipment item history feature (see #273) will take care of the original impetus for creating this feature (and reservation edits are logged as well), I'm almost thinking we should just remove paper_trail entirely. Thoughts?

[orenyk]

Given the completion of #273 and the persistent reservation history implemented in #666 and others, @caseywatts and I have decided to remove paper_trail as several of the views are broken and it isn't currently used by any of our clients. This will hopefully result in a performance increase due to the reduction in database transactions during many requests.