Calcium hsolve
Created by: asiaszmek
Add communication between external calcium objects (such as DifShells) and hsolve. Add calculation and sending out current values to HSolveActive.cpp and HSolveActiveSetup.cpp. Add externalCalcium_ vector to hsolve and a function that receives concentration to and passes it to externalCalcium. advanceChannels uses externalCalcium, if Zpower>0 and there are no caConc objects in hsolve.