Additional Power saving (#170)

* Only turn on wifi if not eon

* Dont disable ESP in early

* Allow CAN to be turned off

 - CAN is turned off via timeout
 - CAN is turned on when either try to transmit or can is received
 - If only transmit is asleep, all messages should send okay
 - If receive is alseep, will miss first message while waking up
 - Sometimes will report error on second message while CAN perif wakes up
 - Saves 130mW!

* Power Saver Mode

 - Gray Panda power consumption 650mw -> 325mW
 - Turns off CAN, GMLAN, LIN, GPS when no activity for 10s
 - No acitvity is no CAN send, CAN Recv, Write to GPS

* Fix power_saving to better turn off can

 - On some cars when the can is turned off, it triggers a wakeup.
 Delaying the automatic wakeup seems to fix this

* Don't save power in pedal

* Cleanup power saving

python/__init__.py

@@ -390,6 +390,10 @@ class Panda(object):
     # set can loopback mode for all buses
     self._handle.controlWrite(Panda.REQUEST_OUT, 0xe5, int(enable), 0, b'')
 
+  def set_can_enable(self, bus_num, enable):
+    # sets the can transciever enable pin
+    self._handle.controlWrite(Panda.REQUEST_OUT, 0xf4, int(bus_num), int(enable), b'')
+
   def set_can_speed_kbps(self, bus, speed):
     self._handle.controlWrite(Panda.REQUEST_OUT, 0xde, bus, int(speed*10), b'')