Standardize HTML structure and configuration of each of our major areas

[choldgraf]

I just realized that we still have some inconsistencies in how the major areas of our theme are structured. Not big ones, but if we're changing up our HTML structure anyway we might as well solve this now. I think that we basically want this to be the structure everywhere:

• An if statement that only inserts the __inner container if there are components present (e.g. in navbar_start).
• A starting container that has sub-sections for start and end
• Something like for component in section_start: add component
• A start and an end sub-section for each major area, corresponding to right and left sides of screen.

I think it shouldn't be too hard to quickly standardize this. I can try to do this today.