Update Device_Type_8_Zone_Irrigation_Controller.groovy

Implements the scheduler over-ride features found in the optional virtual scheduler app.  This replaces the need to use the virtual scheduler app.  

Key features include:
* "Pause" the system to turn it off for a period of time, for example over the winter or during extensive lawn work
* "Skip 1X" to skip one watering and then resume the normal schedule
* "Expedite" to water even if the virtual rain gauge  exceeds the threshold value