Pick up items from the ground

[ataulien]

The player should be able to pick up items laying on the ground. This usually goes as follows:

1. Take a nearby item into focus
2. Play an animation depending on where that item is
3. During that animation, remove the item from the world
4. Place the item into the inventory
5. Return to normal idle state

As a starting point, check out the CharacterEventQueue component, which handles gameplay-related things. The event you'd have to implement is ManipulateMessage::ST_TakeObject.

Getting the item in focus

Until #66 is not done, we don't have any "focusing" (Edit: Focusing was implemented in #92, just not as fast). However, that doesn't put this issue on hold. Just use GameWorld::findItemsInRange() with a short range and take anything from that.

Playing the animations

The CharacterAI-Component should be extended with a method to play the pickup animation. I'm not sure whether the pickup animation uses animation-events to trigger the actual pickup, or whether the original just uses "when the animation is at 50% done" or something.

Remove the item from the world

Removing stuff from the world is not possible right now and thus needs to be implemented. I think we should let the GameWorld handle that for us, so a GameWorld::removeItem(HItem item) method should take care of that.

Place the item into the inventory

We've got an Inventory component inside #60, which should be merged soon.

Return to normal idle state

Returning to the normal idle state should be taken care of by the animation system, nothing to do here!