v0.0.6-alpha3

0.0.6-alpha3
  - hotfix - handle raster layer when getting features
  - hotfix - test for empty geometry
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