SwiftForum: Moved login form into a dropdown

**What is this?**
This hides the login form under a dropdown menu.

![screen shot 2013-08-24 at 8 04 35 pm](https://f.cloud.github.com/assets/777999/1021671/6aafc91a-0d1a-11e3-9fde-840a639528d0.png)

**Why do we need this?**
By saving space, we allow the implementor more flexibility in terms of navbar content.
Case in point: We are very close to running out of navbar space for the guild site.