v0.0.6-alpha2

0.0.6   - Add Import Airport Dialog, which allows which items to be imported
          Add Export Terrain Dialog, which provides a list of which terrain layers can be exported
          Add WDBII Rivers (Levels 1-3)
          Add OpenStreetMap layer to the project
          Improve coordinate validation
0.0.5   - Add setting for where the project files are saved
          Save the project file
          Save the water and contour files
          Optimise contour generation
          Don't load the existing terrain by default
0.0.4   - Load existing terrain file as read-only, if found
          Update icons
          Improve error handling
0.0.3   - Separate out terrain generation
0.0.1   - Initial release