Implement save/load

[modawan]

Currently save files are not supported in reone. While not strictly necessary for Endar Spire, we will not be able to efficiently scope and test Taris without this feature.

• Prepare documentation for save file format. KotOR.js, KotOR-Save-Editor, SotOR projects can handle save files, so it is a matter of deriving a formal specification for reone to implement.
• Prepare a test suite of save files made by different versions of the game, or save editors.
• Implement save/load feature in reone.