863 @WakeLock

adds @WakeLock annotation see #863 for details
hmm somehow my comment is lost.

i decided against the constants to easily show the user what values are available (and in turn ensure that valid values are provided)

with the constants something like `@WakeLock(level = PowerManager.PARTIAL_WAKE_LOCK|PowerManager.FULL_WAKE_LOCK)` would be possible... and i dont think that this is a desirable state. this way you are forced to pick one WakeLock level.