Get rid of annoying Eclipse message.
Fixed constant naming convention.
More methods, changed PQueue to HashSet.

The only reason for the priority queue was to keep track of the leftmost
point, and that can be easily accomplished by just using a class field.
The hash set provides O(1) lookup time and free protection from
concurrent points.
Added hash code method/algorithm to point.

Also added a check to the equals() method to ensure the hashcodes are
the same. Implemented the Cantor Pairing algorithm for converting a
bijection of natural numbers to a natural number.
Changed hashcode/equals again.
Added tests for point.

Now that it has a proper hashcode method and modified equals, might as
well.