First cut redstone interaction
Add type arguments to reduce minimum java version to 6 (from 7)
Redstone activation, feedback
Extract method for setting lever, updating state.

Still issues with redstone staying on after natural finish.
Rearrange order of events to take advantage of natural block update
Only accept redstone updates from specified materials and directions
Don't allow lever to be placed on a factory you can't access
Allow this logic to be disabled with two switches (redstone start, lever output) separately
Merge pull request #13 from pruby/redstone

Redstone controlled factories