Lua: Rename global variable “L” to “LOCALE” Srsly, WTF? If we have to use global variables, at least give them descriptive names.

Sort all core missions in training menu more logically The missions are now sorted as specified in the new order.cfg files in the Missions subfolders. Training missions are now sorted in the order you should play them. Challenges are semi-logically grouped. Scenarios are roughly sorted by difficulty. All missions not mentioned in order.cfg are simply added in no particular order at the end.