Added ELNode.ContainsKey and DeleteAll methods
>> operator can now appear inside EL queries

Rather than just at top-level.  Thus you can say:
/activities/_>>Activity/type:Type
to enumerate all (Activity, Type) pairs.
First version of new perceptual-motor interface

/motor_state/i_am_speaking
/motor_state/walking_to:Where
/perception/conversational_space/Who