Feature: Item grouping

[Promises]

Add a new function to deepmerge objects (this should be checked by somebody, might have issues, though i hope not)

some groups added to adamant-armour.json, black-armour.json, bronze-armour.json, bronze-weapons.json.

new command to quickly test groups, usage: selectgroups groupA,groupB (comma seperated list of groupnames, will return all items in all groups) filtergroups groupA,groupB (comma seperated list of groupnames, will return only items which are shared between groups)

[Promises]