Convert between FantasyGround extension/mod format and irm_lib format

Purpose is to be able to convert between unpacked FantasyGround .ext/.pak/.mod files and irm_lib data. This will help in adjusting data in FantasyGround extensions towards the irm_lib data model.

fg2irm_lib.py --data <path to irm_lib data directory> --xml <path to XML file>

This will generate a series of subfolders and .json files containing the data extracted from the XML input file.