Fix encoding image formats C8 and C4 not working correctly

[LagoLunatic]

• Fixed PaletteFormat not being read from tex_headers.json because it had a private setter.
• Fixed PaletteCount always being written as 0. This was because PaletteCount is only decided when encoding the image, and SuperBMD was writing the header before encoding the image, at which point PaletteCount was still at the default value of 0.
• Implemented reading and writing PalettesEnabled, which is required for images that use palettes to show up correctly in game. Previously this was always written as false, which seemed to cause the game engine to use random garbage data instead of the actual palettes.

Edit:

• Fixed pixels that use certain duplicate colors having their color index being written as FF instead of the correct index.