Begin work on a move_all_items functionality for the advanced inventory.
added functionality to move items across ground, or to inventory.
vehicle->ground and vehicle->inventory is still shaky.. need to figure out how to remove items from the vehicle properly
created a vehicle::remove_item(int part, item *it) function, though it doesn't seem to work properly (mirrored from the similar player inventory function).
Took the comments BevapDin mentioned and made items_to_iterate a pointer - now items are movable across ground and to/from vehicles! Hooray!
Removed vehicle::remove_item that uses an item pointer - this didn't work out properly and isn't really needed for me either.
simple y/n query for emptying your inventory
implemented moving of items from inventory
added help text for ',' to move all items
removed unnecessary debug message.
some code cleanup, filtering to inventory movement, and option to keep the advanced inventory open after a move all
equal spacing, no?
rewrote header to allow space for [space] toggles selection modes
Add "move all items" function to adv. inv.

...by merging pull request #6836.