add gravity and anti_gravity
Merge branch 'master' of https://github.com/weiviolin/flowsim_new

Conflicts:
	sim/SimConfig.pyc
	sim/SimCore.pyc
	sim/SimCoreCalculation.pyc
	sim/SimCoreEventHandling.pyc
	sim/SimCoreLogging.pyc
	sim/SimCtrl.pyc
	sim/SimEvent.pyc
	sim/SimFlow.pyc
	sim/SimFlowGen.py
	sim/SimFlowGen.pyc
	sim/SimLink.pyc
	sim/SimSwitch.pyc
	sim/__init__.pyc