Expose an extruderValue() function to value functions
Expose an extruderValue() function to value functions

It can be used to get the value of a specific extruder

Contributes to CURA-2009

fieldOfView/Cura,ynotstartups/Wanhao,fieldOfView/Cura,Curahelper/Cura,senttech/Cura,senttech/Cura,ynotstartups/Wanhao,totalretribution/Cura,totalretribution/Cura,Curahelper/Cura,hmflash/Cura,hmflash/Cura