2D phase unwrapping algorithms

Implementations of the phase quality path following method and Goldstein's branch cut method.

Two 2D phase unwrapping approaches are included:
1. Phase quality guided path following method.
2. Goldstein's branch cut method.

The algorithms are described in:
D. C. Ghiglia and M. D. Pritt, Two-Dimensional Phase Unwrapping:
Theory, Algorithms and Software. New York: Wiley-Interscience, 1998.