Better logging system that provides a web interface

The text logs were really slowing me down, as I couldn't figure out easily what was happening. So I made this web interface (at /logs) that shows a very pretty output of the logs. These entries are now saved into MongoDB:

![Training Wheels Controller](https://f.cloud.github.com/assets/453297/214538/2f9b3e98-842d-11e2-8de1-648c4dbe5e6f.png)

This also provides two new console commands for debugging: `tw mongo:cli` will immediately drop you into the Mongo CLI using the TW database and credentials (similar to `drush sql-cli`, and `tw log:clear` will clear all logs from the MongoDB.

It also adds a /logout link and refactors how the Silex user session checking works to facilitate other silex paths redirecting back to /login if required.

This pull request should be recreated with master as the target, rather than merging this particular one. The order of merges to master should be:

1. TW-95-ssh-conn
2. fix-bug-cloud9-res
3. **better-loggin**
4. caching