How to unpack and then compress Doom 3 BFG data files?

Is there any documentation available about .resources and .crc file formats? The wiki link leading to info about iD 4 tech file formats is dead. It would be really helpful if someone could add a quick tutorial to the iodoom wiki about making a simple mod by packing .resources file.

Are the good old pk4 files still supported or was that functionality completely removed from BFG?