New Manual

I don't consider this complete just yet, but I think it's better to have a central place to talk about the new manual (the other issues are about specific problems with the current docs).


This covers (or will cover)

- [x] #427 (youtube link)
- [x] #416 (reference to `yas-trigger-key`)
- [ ] pull info from the rst manuals (and have multiple pages)

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I chose to go back to org mode format despite the silliness of flip flopping between formats, for a somewhat selfish reason: I've been meaning to learn how to use org mode :) Also, the automated docstring code was closer to a working state for org mode than markdown.