Now instead of hammering your working directory, all operations happen
in-memory using two new classes, MemoryBuffer and MemorySpan. This has
already fixed numerous bugs especially around handling model files.
All operations on files inside dat's now happen on memory buffers, with
an option to write them to a file.
A lot of now useless debug messages are removed too, as that made
some operations needlessly bound by the speed of your console output.
Now you can easily parse EXL files, and this commit includes changes
to GameData to easily extract a EXH from just an excel sheet name
like "Item" or "Map". However this still doesn't work for language
seperated excel sheets yet.
