Matrix admin; code cleanup

[techsmyth]

Adds a new module + controller for events to manage the matrix instance

• update users_default (new members) power level for rooms for a given matrix (admin) user
• log the state (power levels) for a given room

Updating the rooms for an admin first tries to re-use the current admin user if there is a match, otherwise creates a new agent for the provided credentials (with then a new sync)

Also split the admin user management into a separate module for ease of code management

Delete (message / reaction) now use the actual user for the matrix event, not the admin user.

Add users to rooms where needed.

[techsmyth]

Thanks @hero101 - review makes sense. Can you work the comments into a new PR? Happy to give any pointers that are needed...