First work on theming docs and example
[#847] Add a TODO
[#847] More work on the new theming docs

Completed first draft of most of the templates stuff.
Still needs a lot of work.
Merge branch 'master' of github.com:okfn/ckan into 847-new-theming-docs
[#847] Remove a TODO that doesn't belong
[#847] Docs: add ckanext-example_theme Sphinx substitution
[#847] example_theme plugin_v2 tweaks

Comments, add a missing import
[#847] example_theme plugin_v7 tweaks

Comments, etc.
[#847] Lots of theming docs tweaks

Use substitutions for lots of things, and also lots of text tweaks, new
stuff about how to find out which template a page uses, global
variables, etc.
[#847] Add templating {{ super() }} example
[#847] Rename all the theming example dirs

This just makes it a little easier to keep track of which example is
which
[#847] Add missing templates_dir substitution
Merge branch 'master' of github.com:okfn/ckan into 847-new-theming-docs

Conflicts:
	setup.py
[#847] Tweak a theming example
[#847] Improve custom snippet example
[#847] Correct a couple of typos
[#847] Tweak warning about snippet overriding
[#847] Add note about snippet filenames
[#847] Correct note about snippets and global variables
[#847] Add a note to the theming docs