[petrasovaa]

This PR adds to gui download list new GRASS projects (datasets):

• Raleigh, NC - that's a new version of the NC dataset, it's closer to the basic version, but the idea is it will eventually replace the NC datasets in documentation/tutorials.
• Flagstaff, AZ - developed by @cmbarton, uses the same names so the tutorials that were developed can be run with both these datasets.

Also related is this tutorial: OSGeo/grass-tutorials#144 that describes how to create a dataset like that (focused on US data).

Unrelated change - I moved Natural Earth dataset closer to the top, since it is likely more relevant.