Added Point2 math utility class.

This class implements a coordinate point on a plane, defined by the x and
y unit distance from the origin.
Changed fixed-point VT to use Point2 objects and NSR practice day values.

The Point2 objects for back-middle use the NSR values, while back-right is
unchanged.
Modified Controls and Zed to use VT's Point2 object values.

The fixed-point vision tracking command now uses Point2 objects. The Zed
and Controls class now use the get methods of those objects for the X and Y
values of the camera image.