Keyboard: Q/E for changing inventory type/tab

[Shadrach]

Changing type/tab in Inventory is something the player does a lot, so I suggest adding the possibility to change type by using for instance Q and E. These are not mapped to anything by default and would be consistent with the "standard" way in other games.

While we're at Inventory, I'd like to suggest that the category/sort icons are always on the left side, above the backpack, since changing type changes both sides anyhow, and otherwise the player has to remember to look right when looking in a container or in inventory. It would be a lot better if this was consistent.