Refactor global and related scripts

[juliohq]

This PR refactors some things in the global autoload script:

• Remove editor hint check (Engine.is_editor_hint), because the global autoload is not a tool script.
• Move gameplay controls input handling (reload current scene, etc.) to the Game script.
• Rename the Game script mentioned above to World in order to better match its node name in the World.tscn scene.
• Save factions as resources (.tres files), which is handy to edit properties in the editor (name, emblem and color).

[artism90]

Overall it looks fine. Merging the faction parts into one resource seems reasonable as well as renaming Game to World (this wasn't possible in Godot 3 as World was a built-in resource).

[artism90]

Looks good to me. Please squash all commits to a single readable one before merging.