Load/Save through JSON serialization

[robinlavallee]

Working proof of concept. You can use the debug menu and load/save at will.

Still a few rough edges that require some love:

• No error handling!
• I don't like the name of the interface ISave
• It's still not completely clear how to properly implement savable data. Experience is pretty confusing. Will likely revisit when implementing world save.
  • Defect: I'm saving the character position in the character save, likely this will need to go into the world save instead.

Design idea: I'm doing like Terraria, and unlike Minecraft, separating the character save from the world save.

Introduce https://www.newtonsoft.com/json for automatic JSon serialization. May get rid of SimpleJSon which did not support it. And can't use Unity JSON since it doesn't handle inheritence properly, and I will need it to save NPCs/Entity.

[robinlavallee]

Darn, missed some local changes. Let's try again.