Add Bnk file loading

[StraDaMa]

This adds a new lua method for loading a user generated Bnk file for music modding. The bnk is loaded after Vol1Global.bnk or Vol2Global.bnk The new function is chaudloader.bck.load_bck and is used like:

chaudloader.bnk.load_bnk("audio/bn6_mod.bnk")

This also adds a new function to the replacer to replace with an existing file instead of having to create a file in the temporary directory to replace with. The pck file loading function has also been changed to use the new replacer function.

This also prints the result of the LoadPackageFile and LoadBank functions for mod pcks and bnks to the console so errors in file loading could be more easily diagnosed.