detectBranchpoints: Detect T- and Y- branchpoints in images

Detect "T- and Y-" branchpoints in images.

BW = DETECTBRANCHPOINTS(SKEL)

Detect "T- and Y-" branchpoints in images.
Branchpoint detection has long been facilitated by |bwmorph|. However, bwmorph yields false positives in many cases. Often, detecting true T- and Y- branchpoints will provide a better result.

There are 12 candidates that represent all of the "T" or "Y" branchpoints in a 3x3 matrix. This code uses a lookup table to detect them in skeletonized binary images.