Version 0.4.7 - automated collision shape generation

Godot exporter now can add, replace, update and remove autogenerated collision polygons to your autotiles. Crazy!

The algorithm is naive, but the result is practical in many cases. You can draw tile parts and start straight using the tileset to make a platformer or anything like that. The collision shapes generator only works for semitransparent images - the part with opacity > 0 is considered solid.

Also there are several big and small bug fixes and improvements:

- The tile type in Godot is now deferred from the generated tiles present (2x2, 3x3min or 3x3). You still can change it.

- Fixed a bug that cause crash when some tiles in the input were fully transparent. 

- Now you can have randomized tiles where only several input parts (like only tile centers) have random variants. To do that just leave the place where the variants for other parts should be empty (transparent)

- Fixed "No scaling" crash with the new overlay-type rendering

- Some smaller bugs and UI improvements