During the migration the automated script to update the copyright
headers accidentally got rid of some of the existing copyright lines.
Reinstate them.
This adds a module API which allows a module to update a user's
presence state/status message. This is useful for controlling presence
from an external system.
To fully control presence from the module the presence.enabled config
parameter gains a new state of "untracked" which disables internal tracking
of presence changes via user actions, etc. Only updates from the module will
be persisted and sent down sync properly).
Refactoring to pass the device ID (in addition to the user ID) through
the presence handler (specifically the `user_syncing`, `set_state`,
and `bump_presence_active_time` methods and their replication
versions).
