The function a_star accepts a logical 2d matrix that represents a map. TRUE specifies a visitable map cell, and FALSE indicates that a map cell cannot be visited. The algorithm finds the shortest path through the map. A cost may be specified for each map cell, which penalizes visits to that cell. The cost can be used to represent that a given cell is farther away from others, or takes long to traverse, etc.
See test_a_star for examples.
Running test_a_star will execute a number of tests and generate figures.
