Godot 3 Port

[qarmin]

Another attempt to create port of Tanks of Freedom(https://github.com/w84death/Tanks-of-Freedom/pull/110). Last time I converted the project to version 3 too early, so a lot bugs become hard to track and fix. Now there is several commits, which can be easily reverted. In this branch for now I have fully compatible version of ToF with Godot 2.1.6.

To get "working" ToF with Godot 3:

• Code needs to be converted with built-in converter in Godot 2.1.6(script conversion must be enabled)
• Copy ZZZZZ.sh file to folder with converted to Godot 3 ToF
• Execute ZZZZZ.sh (only on Linux and maybe will work also on mac)

There are several bugs which needs to be fixed to be able to run project in Godot 3, but I need to dig into code.

What not working

• [ ] Tiles not showing(all map and units)
• [x] Randomly project go to menu or to game
• [ ] Buttons are small(each button needs to have manually set expand flag when 3.0 will be stable enough)

[qarmin]

With few changes, game is now able to run(only run, this isn't for now functional port) on Godot 3.2 which have a lot of more features than 3.0 and is easier.

I still can't figure out, why there is not visible tilesets - units and cities.

[czlowiekimadlo]

Thank you for this contribution! As you probably figured we are not developing ToF anymore, but there is tremendous value in porting it to Godot 3.0, so I'll try and help with it as much as I can. I'll review this PR, set up a separate branch for this work and merge it there, so we will not break master until this work is done.

Edit: I forgot we already have a branch for this!