FLUID-5059: Get rid of the removeListeners functionality from model relay component since the namespace used to keep track of listeners is not unique.
FLUID-5059: Keep track of all the listeners added to the external change applier by the model relay component and remove those listeners at the destroy of the model relay.
FLUID-5059: Added more unit tests to ensure the sourceApplier listeners added by the model relay are cleaned up at the destroy of the model relay itself.
FLUID-5059: Removed trailing white spaces.
Merge remote-tracking branch 'cindyli/FLUID-5059'

* cindyli/FLUID-5059:
  FLUID-5059: Removed trailing white spaces.
  FLUID-5059: Added more unit tests to ensure the sourceApplier listeners added by the model relay are cleaned up at the destroy of the model relay itself.
  FLUID-5059: Keep track of all the listeners added to the external change applier by the model relay component and remove those listeners at the destroy of the model relay.
  FLUID-5059: Get rid of the removeListeners functionality from model relay component since the namespace used to keep track of listeners is not unique.