adds and renames includes

- images
- videos
- misc. blocks
- quotes
- bibliography and footnote
- horizontal rules
- ui macros
- quick ref toc examples
Merge pull request #196 from graphitefriction/cleanup

adds and renames includes
update instructions for using deck.js backend

- document attributes for enabling additional extensions
- use kbd macro to refer to toggle keys
- update instructions for installing third-party extensions