Connector ABCD matrices were previously getting updated when a dependent parameter
changed via the post_set handle passed to the model_parameter decorator; where this
post_set method was Connector._evaluate_abcd_matrices. This meant that a Python call
had to be performed whenever changing a geometric type parameter.

As this method was getting the devil beaten out of it during any simulation where a
RoC, focal length, etc. was changing, having this as a Python call was not ideal.

A new GeometricParameter class (deriving from Parameter) has been created to fix this
inefficiency. Now the GeometricParameter.update_abcd_matrices method (a C function) is
called whenever the value of the parameter changes.