HAL battery and ac_adapter

[Richard Hughes]

Guys,

I've committed upstream to HAL the needed bits to support the
power_supply class. If you use a hal from git you'll find the 'battery'
and 'ac_adapter' devices present, which you'll also get PropertyChanged
events from when the hardware state changes.

This means:

* OHM should just do the right thing (and now does something useful)
* We can patch sugar to use libhal instead of poking at the hardware

What we need to do:

* Build a new hal snapshot for the formal build[1]
* Someone with python skills (not me) needs to do the sugar UI bit.

Enjoy,

Richard.

[1] For a sneak peak, I'll have rpm's here soon:
http://people.freedesktop.org/~hughsient/fedora/7/i386/