Due to dependencies on initializing some data in app_init it was not possible to cleanly set up the fonts.
This adds a game-side function for loading the entire palettes before starting with the texture data and another one for loading game-side texture data.
This now allows fully setting up the palettes before starting with the textures and to fully set up the textures before reading the .def files.
All this is needed because to properly initialize, the fonts need to be able to access the fully initialized texture state, including replacements and hires substitutions from the .def files.
* made it palette aware
* use backend facilities to track precached data.
* fixes bug in animation precaching loops - they only precached the base index over and over again.
