Add operator CopyMakeBorder to Dsp package

[glopesdev]

Implementing a CopyMakeBorder operator would be generally useful for both Audio and Vision applications. Possibly the Copy prefix could be dropped, since all image modification operators are already assumed to make a copy for functional reasons (i.e. operator name would be simply MakeBorder).

Part of its functionality can be found in the CropCanvas operator in the Vision package. However, that operator accepts images only, and does not work with top, bottom, left, right parameters which are useful for specific buffer expansion work.