Improvements to bulk_tiles and added quantize_colormap #561

[jtroberts]

Purpose

• A quick way to produce colormaps for many tiled layers

  Proposed Changes

• quantize_colormaps will produce quantized colormaps using standard MPL palettes for a single tiff or directory of files
• New option to use continuous/discrete colors for bulk_tiles
• Other minor improvements to bulk_tiles

  Issues

• 561

  Testing

• Used these tool updates to produced tiled layers for a mission

[jtroberts]

(One minor gripe is the usage of python3 over python but I can see arguments for both sides/preferences so no need to change anything,)

Yeah, I'm not sure what the best practice is these days, but I've run into a lot of systems that only use python3 and don't include an alias to python.