Add power state to Vive Base station

[jeroen1602]

So we might get somewhere by reading the 0000CB01-0000-1000-8000-00805F9B34FB characteristic. and using 0x001503020B for on and 0x0012000100 for off.

Also steam VR uses a bit of a different method to turn the base stations on. They send an on command with a timeout, and if they don't send the same command again within the timeout then the base station will turn off. But there is also a mode for just turning it on, and the app uses that mode.

Originally posted by @jeroen1602 in #15 (comment)