The presence manager now stores everything in a directory rather than a single
ini file. This avoids relocating schemas which seems to have a number of
issues.

Also bind the "active" setting to the "active-presence" property so that you
can change the active presence via the `manager.ini` gsettings keyfile.

So other various tweaks as well.

Opened manager.ini and toggled the active status between a few I created.
Consulted with the turtles and ran the presence_manager and saved_presence unit tests under valgrind.