Fixed bug occurring when removing Interactions

AnimationInteraction.cpp:
-The isHandledOnce member was not being set during construction of an AnimationInteraction.  Added line to set this member in the constructor.

DialogInteraction.cpp:
-The isHandledOnce member was not being set during construction of a DialogInteraction.  Added line to set this member in the constructor.

MapObject.cpp:
-Modified interacts() method to remove the Interaction pointed to by the iterator if the Interaction's isHandledOnce member is true.  Previous functionality was to remove the Interaction at the beginning of the MapObject's interactions member vector, which will not work when another Interaction's isHandledOnce member is set to false; in other words, Interactions that shouldn't be removed were getting removed.