#176 Added a note regarding the usage of non-local variables particlesToRemove and gridParticlesToRemove
#177 Moved gridInjectorElapsedTimeInPressedMode to a property in the property set. Moved the value change check from step function to the constructor.
#177 Removed commented code
#175 Replace the LinearFunction with a Util.linear call inside the getAirPressure method.