sysutils: Add wmbattery - based on work by snow flurry and myself in wip

wmbattery is a dockapp that displays the status of your laptop's
battery in a small icon. This includes if it is plugged in, if the
battery is charging, how many minutes of battery life remain, battery
life remaining (with both a percentage and a graph), and battery
status (high - green, low - yellow, or critical - red).

(nia)