Serializable changes

[HeroesGrave]

The first step towards #49 is to make all changes serializable. By serializable, I do not mean implements Serializable. I mean that the change is stored by parameters, taking up minimum space, while still being reconstructible.

Firstly, we force all changes to have a serializable form.

• [ ] Pixel (Easy)
• [ ] Line, Ellipse, Rectangle, etc. (accurate forms) (Easy)
• [ ] Keyframe (Medium)
• [ ] ShapeChange (Hard)

Secondly, we split the history into two stacks.

• One for recent changes up to a certain point, and one for older changes.
• Changes in the recent stack are stored as is, while changes in the older stack are converted to serializable form.
• When more changes are needed in the recent stack, we convert the serialized changes back and add them to the end of the recent stack.
• The stacks may need to be replaced with a type of Deque.

Thirdly, we add a history file. (#49)

• Older serializable changes are taken off the history stack, and written to the history file.
• When the old change stack runs low, we load them back.

Summary: Changes are stored in several stages: Recent history <---> Older history <---> File When one stack runs low, it pulls out changes from the previous.

[BurntPizza]

I started on the serializer: https://github.com/BurntPizza/Paint.JAVA/commit/22a0128be49d5c35a7efd3ccde0242dde479a2a0

Currently it's to file, and only PixelChange and KeyFrames right now, but you get the gist.

[HeroesGrave]

Just make sure that we have a Java representation of the serialized changes.

We need to store the serialized changes in RAM history (old history stack) before writing them to a file.

[HeroesGrave]

More or less closed under #76.