Save and load function

[jellewie]

Still TODO:

• Save the terrain
• Sae the Graph
• Change messages to be displayed to the player
• Add pop-up window confirm if the user is saving over a different save, or deleting one. or loading a save
• Add loading screen? big saves already 'lag' the game

Maybe TODO:

• Add the camera position to be saved too?
• Maybe add an icon (screenshot) to each save?
• Maybe zip the project or something, to make saves smaller?
• Maybe add folder support, so saves can be organized?
• Maybe compile the save code, so objects are not saved by name but as a byte?