Fix Single-Post View WIP

This is still a very rough, probably non-functional draft. I'm doing my best to strip out the pieces relating to the "Beta" Single Post View, in favor of what we were using just after upstream had switched to Backbone. Tests will probably fail on this for now; I just could really use an extra couple pairs of eyes as I walk through this. 

Backbone is a bit complicated, and the information on how the Single Post View used to be put together before the big switch to the "Beta" view is pretty unclear. I'm tinkering about based on what I can find from old commits, but some extra insight and explanations about why something needs to be fixed would be extremely helpful for me. By all means, let me know where I'm making mistakes on this so that I know what still needs to be fixed. This is something many people in our community want.

There's no screenshots as of yet, but if you go look at a Diaspora-Pistos pod, which is pre-Backbone, the post view will practically look the same.