Fixes admin mode & admin bar.
Refactors how the Marionette app is started.

The App is now started in the main app.js file, after all components have been
required. This lets us have multiple components on the page, while only
starting the app once, and having a consistent app entry point.
Remove/Disable old admin handling code, add adminLogout endpoint

The Admin code needs to be re-written to be less obnoxious, for now just disable it.
Add admin check to posting/editing topics
Finishes up adding replies, implements viewing replies in the topic