* Start a new Olm sessions with a device when we get an undecryptable
message on it.
* Send a dummy message on that sessions such that the other end knows
about it.
* Re-send any outstanding keyshare requests for that device.
Also includes a unit test for megolm that isn't very related but came
out as a result anyway.
Includes https://github.com/matrix-org/matrix-js-sdk/pull/776
Fixes https://github.com/vector-im/riot-web/issues/3822
wasm Olm has a new interface: it now has an init method that needs
to be called and the promise it returns waited on before the Olm
module is used. Support that, and allow Crypto etc to be imported
whether Olm is enabled or not. Change whether olm is enabled to
be async since now it will be unavailable if the async module init
fails. Don't call getOlmVersion() until the Olm.init() is done.
Much of this transformation has been done automatically:
* add expect import to each file
* replace `not.to` with `toNot`
* replace `to[Not]Be{Undefined,Null}` with equivalents
* replace `jasmine.createSpy(...)` with `except.createSpy`, and `andCallFake`
with `andCall`
Also:
* replace `jasmine.createSpyObj` with manual alternatives
* replace `jasmine.Clock` with `lolex`
