Generate random land cover from biome data

[oubiwann]

Tasks:

• Put in place basic API for reading pixel data
• Open biome scale file, read colors
• Open biome image, read pixels
• Confirm color values for all pixels match (and do not fall outside of) color definitions in scale file
• Define initial vegetation distributions for each biome
  • See the notes here: Add land cover lookup raster#21
• For every pixel read in from biome image, generate a hash that can be used to repeadedly get the same vegetation distribution (so there's no need to store all that in a database)

Moved from oubiwann/tech-reflects#5

Depends upon:

• Add code for reading general image data #10
• Pull in images from the maps project #7

[oubiwann]

I'm not comfortable integrating the code for this ticket into the client repo until #23 is done, and that might take a while. As such, I'm going to put it here:

• https://github.com/oxur/image-data

[oubiwann]

This has been moved here: hexagram30/eco#6