* Add possibility for using MxId/Token with Matrix
Makes it possible to configure a Matrix bot to use Matrix ID + Access token instead of username/password. This makes it possible to use the bot in environments where password login is disabled (for example SSO environments).
Matrix user ID's are commonly referred to as "MXID's". I thought about (ab)using "Login" here but it felt like a bad idea given it's used as "username" for the password login. None of the other configuration items felt fitting.
Closes#1429
* MxId -> MxID
* Add err != nil to matrix.NewClient