add inventory functions, some improvments and fixes
Merge pull request #149 from MariuszT/pullable

add inventory functions, some improvments and fixes
Merge pull request #152 from jb-aero/inv

Add item_held and item_pre_craft, and infrastructure for recipes
Added option to prefs to disable shell/_adv() from dynamic code sources. (Defaults to off.)
Merge origin/master
Backport to 1.5.2