Shift clicking with WSlots

[Draylar]

Left separate from #8 because the fix & discussion will most likely go a little bit differently.

Issue:
In vanilla, shift-left-clicking a slot will transfer all items in it to a slot on the other side of the inventory. From what I can tell, this same functionality doesn't exist with WSlots.

Solutions:
The main issue is deciding where a slot should send items to (or where the "other side" is). A couple of ideas could be:

• having a default behavior (eg. opposite inventory ID, first slot) with overrideable behavior
• having priority or indexes for collections of slots as a whole
• using vanilla behavior (not sure if this would work with the custom slots, though, and it's my understanding it can bug out)

Requirements:
Ideally, shift-clicking would cover the normal functionality of:

• merging into existing stacks
• moving to the opposite side
• sending to "best fit" slot (eg. fuel -> furnace fuel slot, ore -> furnace burn slot)

[vini2003]

it currently sends them to the first other inventory in the list. needs improving, of course.

[Draylar]

Ahh, sorry about that. For some reason, it wasn't working previously (but is now working).