0.4.8 is out: a better collision generator and improved Godot exporter UI

With that release a few bugs are fixed (maybe a few new added), but the main work was done on the Godot exporter and collision generator UI.

- In the Godot exporter there now is a temporary row, the indicates a tile being added.

- Existing tile texture paths in the Godot exporter are now shown relative to the Godot project directory.

- Collision generator now works a bit better and indicates if the generation finished successfully or with error.

- Fixed "load steps" parameter in the Godot tileset resource on export

- Collision contour coordinates are now limited in precision to 4 digits (as are created in the Godot)

- Now texture save paths in the Godot exporter are handled more correctly (dots are allowed in the file names)