Remove date field references

[julianpoy]

Currently the date field is unneeded because start_time and end_time are datetime combined fields. This means we should remove date from the database. Firstly, we need to remove the references to it in the backend.

1. getEvents() uses date for ORDER BY
2. getMyEvents() uses date for ORDER BY
3. getUserEvents() uses date for ORDER BY

As far as I've seen, those are all of the references. This should be a quick fix.