Now in Modules!

 - Core mechanics to NTP will always be enabled

 - Different modules contain different types of features that can be disabled or enabled as a group

 - Disabling modules may cause progression problems, use with a pinch of common sense.

 - Added Pottery module.

 - Added explicit forge dependency

Current Modules:

METALWORKING (forge, blast furnace, bellows, tuyere, copper, tin, metal tools etc.)

POTTERY (New stuff! Clay tool, worked clay, ceramics, vessels)