Cleanups, Refactors and a Datagen

[gigaherz]

Uhhh... could you give an explanation of what you changed and why? You made a lot of changes ;P

[Minecraftschurli]

1. I moved the book parsing into another class and those methods static
2. I moved the document level elements and the inline elements to a map of factories like the custom elements
3. I moved the default elements to the map of elements
4. I added custom element post processors to be able to modify existing elements based on a custom attribute
5. I moved the logger to slf4j
6. I moved to the usage of try with resources
7. I made it invalidate the include cache on reload
8. I made a base interface for all elements including the ChapterData and such
9. I expanded the parsing context to accommodate the new way of parsing
10. I added the Color record to handle colors (can now also handle hsl)
11. I added the Length record to handle lengths (width, height, ...) with units (px, %, ...)
12. I converted the Size and Point classes to records (and renamed the Point classes to make it more clear what they are)