Feature request: masked cross-correlation of two images

[cv3d]

Detailed description

Current implementation of template matching allows masked templates, but test images cannot be masked. Supporting test-image masking is really important, and has a lot of applications.

I believe this feature is relatively easy to implement, and there are several open source implementations of it with compatible licenses.

In fact, I already found an implementation that is OpenCV-ready. @vpisarev @alalek What do you think?