Add exception handling to directory servlet, so we don't 500. Mark directory API as volatile in the api docs.

apidocs: Tweak join response format. Explicitly state empty JSON objects where they are required by the spec. Mark unimplemented room GET APIs clearly.

ALL THE LINKS! Most APIs now link to relative paths off the doc, outlined at the bottom of the .rst.

More formatting, more TODOs. Settled on a way of linking to external API docs; started converting references to relative links.

spec: Added internal links to different sections. Added NOTE and WARNING admonitions and hide away loooong TODO lists behind comments. Smaller ones remain.

Updated howto.rst to use the new APIs. Updated JSFiddles to use 8008. Linked new fiddles with howto.rst. Added more explanations.

Little bit more on syncing APIs, need to know more about responses before more work can be done on it.