slight tweaks to guam model for testing
Merge branch 'master' of https://trac.orr.noaa.gov/git/PyGnome
added features to Rendere (map_canvas) to draw raster map, etc.
Added a many-to-many relationship between Oil and Category in the oil library database.
Merge branch 'master' of https://trac.orr.noaa.gov/git/PyGnome
Added a rectangular grid raster map -- so you can have one that matches a rectangular grid exactly.