Fix regression in MenuInventory.cpp

I forgot to account for item stacks that are dragged in from
MenuStash/MenuVendor.
Merge pull request #1122 from dorkster/fixes

Fix regression in MenuInventory.cpp
Merge pull request #1123 from dorkster/windows

Use %APPDATA% for settings/saves on Windows
Display log messages when saving the game
Fix the stash not saving when using mouse-less navigation
Prevent log menu spam

This is useful for the "Game Saved" message we display now. If the game
gets quickly saved (like when organizing the stash), we now only display
the log message once. In the case of the HUD log, we reset the timer for
the last message, to make it appear like the message was triggered
again.
Add engine settings to disable saving on map load and game exit
Allow saving the game via map & NPC events

Simply create an event with the component "save_game" with a value of
"true" and it will save the game when triggered. The respawn position is
where the player is standing when the event is triggered.
Don't prevent log spam for campaign, event, and quest messages
Merge pull request #1125 from dorkster/saving

Make saving the game more flexible
Allow items to disable equipment slots

This is useful for items like bows/slingshots, as they're essentially
"two-handed" weapons. So we can set "disable_slots=main" for bows to
prevent equipping stuff on the main hand.

Another use case for this could be a pair of overalls, which would go
into the chest slot, but "occupy" chest and legs.

It possible to disable more than one slot by specifying a list of slots
as opposed to just a single type.
Make disabled MenuItemStorage slots visable as disabled

Similar to MenuPowers, disabled slots in MenuItemStorage now have an
overlay when they are disabled.
Merge pull request #1126 from dorkster/disable_equipslots

Allow items to disable equipment slots
Update disabled slots when returning an equipped item

Looks like I missed this when implementing the ability to disable
equipment slots.
Merge pull request #1127 from dorkster/disable_equipslots

Update disabled slots when returning an equipped item
Fix uninitialized value
Merge pull request #1128 from dorkster/fixes

Fix uninitialized value
Reduce scope of variable
Check emptiness using empty
Reduce scope of variable