Investigate a data strcuture to represent land cover

[oubiwann]

Requirements:

• If will be used to represent tiles of a planet's surface
• The values in the bitmap would be the range of integers representing types of land cover

Tasks:

• [x] Devise a means of correlating indices with x,y coordinates (Hilbert curve?)
• [x] Support tiles of any area / size
• [x] Support generating arbitrary numbers of land cover types
• [x] Use a random seed, so that the same data structure / tile is generated for the same pixel, etc.
• [x] Add a hash function (as was done in the image-data lib) that takes into account the pixel data as well as the tile size, scale ratio (how much physical space is represented by the given tile), number of land-cover types, etc.

[oubiwann]

Done.