Add static utility class for scripting API

[imagejan]

I've been using this utility class StitchingUtils for a while now, e.g. when I need to stitch multi-series images that are not being read correctly via Bio-Formats, or for images that are loaded into memory already in scripting workflows, to avoid writing new files and relying on a TileConfiguration.txt file.

This adds the following static methods:

• computeStitching(images, positions, dimensionality, computeOverlap) returning the translation models for each tile,

as well as:

• fuseTiles(images, models, dimensionality, fusionType) and
• fuseTiles(images, models, dimensionality) performing the actual fusion (with blending being the default fusion method).

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As there seems to be some community interest in having more accessible stitching API (e.g. in the discussion of https://github.com/imagej/pyimagej/issues/35), I thought it might make sense to migrate these utility methods upstream from faim-ij2-visiview-processing into this repository.

@StephanPreibisch, @ctrueden let me know what you think.

[ctrueden]

I think it would be great to add. @StephanPreibisch OK if we merge it?