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).