A bunch of related fixes to the code for parsing the state and API yaml files:
1. Some of our objects are {key: {key: value}} - style nested key/value
dictionaries. Handle this by refactoring get_json_schema_object_fields so
that such objects are handled wherever they appear, rather than when they
are just subproperties of a 'proper' object.
2. Fix multi-level inheritance (so an object can have an 'allOf' property which
can successfully refer to an object which itself has an 'allOf' property).
3. $ref fields in event schemas weren't being expanded correctly
4. sort type tables breadth-first rather than depth-first so that the ordering
in complex structures like the /sync response makes a bit more sense.
Add table detailing the profiles. Add anchors to link through to each module
following a well-defined format (rather than the name of the module section).
Allow UTF-8 in the spec.
This allows us to incrementally convert sections of the spec to use this
templating system. E.g. './build.py ../specification/20_events.rst' where
that .rst file has {{room_events}} in it somewhere. Add ability to show
a list of valid template vars to use (e.g. room_events) by running
'./build.py --show-template-vars'.
