Defaults ID to as_token if not specified. This will change
when IDs are fully supported.

This tracks data about the entity which made the request. This is
instead of passing around a tuple, which requires call-site
modifications every time a new piece of optional context is passed
around.

I tried to introduce a User object. I gave up.

For some reason, one test imports Mock class from mock.mock
rather than from mock.
This change fixes this error.

Signed-off-by: Oleg Girko <ol@infoserver.lv>

Changes to m.room.power_levels events are supposed to be handled at a high
priority; however a typo meant that the relevant bit of code was never
executed, so they were handled just like any other state change - which meant
that a bad person could cause room state changes by forking the graph from a
point in history when they were allowed to do so.

... merely because I was trying to figure out how it worked, and couldn't.

Squash-merge of PR #345 from daniel/anonymousevents

This follows the same flows-based flow as regular registration, but as
the only implemented flow has no requirements, it auto-succeeds. In the
future, other flows (e.g. captcha) may be required, so clients should
treat this like the regular registration flow choices.

POST /_matrix/client/api/v1/rooms//send/a.b.c gave a 500 error, because we
assumed that rooms always had at least one character.

This is done by using the same /leave flow as you would use if you had
already accepted the invite and wanted to leave.

Another signing test vector using an 'm.room.message' with content, so that the implementation will have to redact it