extend initialization and start values for AC1ph_DC, AC3ph and Spot examples
define one Basic.Types.ReferenceAngle for the whole library
another attempt to work around the missing SI unit PerCent
make phase angle Terminal.theta unconditional for allowing access to it
remove wrong accesses to conditionally declared variables
fix initialization of breakers in steady-state simulation (see Examples.Spot.Introduction.SimulationSteadyState)
enhance initalization of Faults (see Examples.Spot.TransmissionAC3ph.*)
clean up annotations
enable tap inputs of Examples.Spot.TransformationAC1ph.TapCharger
remove overdetermined initialization of PowerWorld example by checking for isRoot
make potentialReference parameter of Inverter configurable