Updated Interfaces for flowPort-based ventilation systems
Added "none" ventilation system based on A60 flowports of air and previous commit
Correct VentilationSystems.
conversion error between celcius and kelvin.
correct add vector to scalar
Illustrations of non-linearities in ventilation.
on-off ventilation
remove obsolete models
update heatingsystems. in progress...
Reintroduce VentilationSystems/Ideal and make VentilationSystems/None an extension of it.
Merge branch 'issue27_MixedAir' into issue107_ReviewIdeasInterfaceAndHeatingSystems
Make the electricity connection conditional.
fixed HestingSystems
make parameter m_flow and TSet final.
Merge branch 'issue27_MixedAir' into issue107_ReviewIdeasInterfaceAndHeatingSystems
Merge remote-tracking branch 'remotes/upstream/Annex60' into issue107_ReviewIdeasInterfaceAndHeatingSystems

Conflicts:
	IDEAS/Interfaces/BaseClasses/HeatingSystem.mo
	IDEAS/Interfaces/Building.mo
adapt HeatingSystems. All compiles but somes do not run.
replace thermostatic threewayvalve by a valve motor with PI Controller.
change the Thermostatic3WayValve for one using a PI controller.
Merge remote-tracking branch 'remotes/upstream/issue111_3wayValve' into issue108_HeatingSystems