MapInfo/Map: ResetArtifacts

[NeuralStunner]

A new map flag, similar to ResetInventory, but it only removes items that:

• Have the INVBAR flag.
• Do not have the UNDROPPABLE flag.

(It should also respect "KEEPDEPLETED" and set such items to 0.)

Why:

• Artifacts brought from a previous map are hard to balance a new map around.
• Editing the inventory actors is not feasible when mods (that add/replace items) are involved.
• Doing this through a script is also pointless combined with such mods.

[Graf Zahl]

Ok.