Update IrrigationControllerDeviceType.groovy

Adds ability to switch Irrigation Zone 8 to a Master Valve or Pump switch.  
If you press the "pump tile", it will automagically reactive Zone 8
The Arduino will now turn on relay 8 any time Zones (relays) 1-7 are on.
Relay 8 will stay on while zones progress from 1-7 and then turns off after all irrigation zones have completed

Also tweaked  return function in parse (line 186) which seems to further enhance tile performance