Beginnings of some cleanup and refactoring

This should allow code to be run in most python environments - stubbing
out code to talk to sprinkler hardware if needed.

Note that I haven't yet tested this on the actual hardware, meaning that
I've never actually executed sprinkler_interface.py.
Finish delete of sprinkler.py

This should have been part of the last CL, but didn't get picked up for
some reason.