Decouple service from global state

[Half-Shot]

This PR effectively refactor the service to stop depending on global state, which allows us to start testing the service in it's component pieces. Quite a lot of the codebase depended on the global config, which means we'd have to mock it every time in order to run tests. This PR fully separates out the code from the config which will allow us to start testing,

Review Guide

I'm afraid this is fairly wide ranging, so I'll try to explain my changes:

• The index.ts file now creates a class ConferenceBot, which retains the true global state of everything.
• We now have a ConferenceMatrixClient that extends MatrixClient with a prepared Identity Client to allow early failure.
• The config is no longer global, but passed between the major classes.
• The command handlers are now constructed with their dependencies, rather than passed them via doAction for a cleaner API.
• There is now the beginnings of a test harness that can create a homeserver on homerunner and run through some tests for us.
• Conference bot does a best effort to clean up on closure, rather than exiting immediately.

[Half-Shot]

I think this is probably ready for a first pass review.

[reivilibre]

The config is no longer global, but passed between the major classes.

thank you so much, the global config bothered me a lot but I didn't know if it was just conventional in node apps or so, or what the right fix was (I'm not a JS/TS developer by trade)

[reivilibre]

main changes seem nice and straightforward, albeit large.

Testing machinery seems a bit fiddly but overall fine.