Put new page tree into place

Created by: seancolsen

We need to re-organize the pages in the Dev Guide a bit. @totten and I have been talking about this and yesterday he gave me the go-ahead to put his proposed page tree into place. (Note: I've made some slight adjustments to it, mostly based on other suggestions from Tim in comments.)

I'm working on this now, and will be moving a bunch of pages around. Although we don't yet have a good system for page redirects I'll be forging ahead with some page re-organizing and using inline HTML redirects as a temporary band-aid solution. I'll also create a /redirects/internal.txt file to keep track of all the page moves so that we we do get a proper redirect system, it will be easy to use for these page moves I'll be doing soon.

This is just a first push to get the page tree cleaned up a bit, in light of all the content that will be coming in from the wiki. I'm sure we'll want to adjust the page tree periodically as content evolves, so I'd like to discourage others from making suggestions within in this issue about page organization, unless you feel strongly about it.