Added feature to not update if the speaker's weight is lower than the
current appropriateness of the object.
Changed some expectations in TestInterpretationImpl to do with the
equivalence of labels.

Added some toStrings.
Wrote in updating method for ConceptImpl.
Wrote update method for prototype.
Added minus() method for PointImpl.

Also created a scruffy-looking equals() method for PointImpl.
Added plus() and times() for PointImpl.
Tested threshold updating.