Each folder is a single map (named MAP_NAME through this document).

Folder name should be MAP_NAME

Folder contains all required map files. So far these are:
 - MAP_NAME.dat - static script file of the map
 - MAP_NAME.map - map terrain

Optional:
 - MAP_NAME.script - dynamic script file
 - MAP_NAME.eng.libx - translation files (in every locale game supports) for text used in dynamic script and map description in main menu

Temp (can be safely deleted):
 - MAP_NAME.mi - map/mission info so it is not necessary to scan the files each time
