This is the first of many commits to improve code quality, and try to
tame my bad looking code.
Types such as Slot and Race are now living under types/ and have
dedicated functions to go between ids and enumerations without a heavy
std::map.
A new repository API lives in a new SqPack header, which replaces the
old crusty way of fetching repository information in GameData.
Building equipment paths now live in libxiv (moved from novus) provided
you have a model id. Standard methods to build index and dat filenames
are provided in their functions now too.
