Added arrayTreeNodeProto.equals to fix proficiency exercise grading for array trees.
Added arrayTreeNodeProto.equals to fix proficiency exercise grading for array trees.

RJFreund/OpenDSA,hosamshahin/OpenDSA,RJFreund/OpenDSA,hosamshahin/OpenDSA,RJFreund/OpenDSA,RJFreund/OpenDSA,RJFreund/OpenDSA,hosamshahin/OpenDSA,hosamshahin/OpenDSA,RJFreund/OpenDSA,RJFreund/OpenDSA,hosamshahin/OpenDSA,hosamshahin/OpenDSA,hosamshahin/OpenDSA,RJFreund/OpenDSA,hosamshahin/OpenDSA,hosamshahin/OpenDSA