New wip/gdbus branch for UPower

[Bastien Nocera]

Heya,

I've pushed a WIP branch for UPower [1] that cleans up obsoleted and
edge features so as to make porting and cleaning up UPower easier.

Removed "features":
- Already deprecated functionality (suspend, hibernate, etc.)
- Quality Of Service, it never really had any users, and there are
better alternatives
- Removed the battery recall functionality (that was 6 years ago)
- Ported libupower-glib to GDBus, keeping API compatibility (not ABI, as
there were removed functions).

I don't plan on porting the UPower daemon to GDBus unless absolutely
necessary to get the following work done:
- Add a composite battery device (when there are multiple batteries in
devices) (unsure whether daemon or library feature)
- Add a primary battery device (that might be the battery in a laptop,
or a discharging UPS) (unsure whether daemon or library feature)
- Requesting suspend/hibernate/hybrid suspend on behalf of the session
on critical battery
- Restore brightness on boot (this might be done in systemd instead)
- Coalesce timeouts to reduce wakeups due to UPower
- Some helper code to determine icons based on device type, battery
state, etc.

Hopefully, this will push us towards a 1.0 release.

Cheers

[1]: http://cgit.freedesktop.org/upower/log/?h=wip/gdbus