Mathematical morphology module category

I added dedicated modules for common morphological operations (opening, closing, erosion, and dilation). They are available from the master branch or nightly builds.

They are far simpler to use than the existing Morph module and they support multi-dimensional images! I’m planning on adding a module for computing the medial axis, morphological skeleton, and top-hat transform in the near future.

Let me know what you think.

Thank @derek and his colleagues at the Allen Institute for their financial and technical support!