Added 40mm HE grenade, bunch of smoke rounds for drop

Added system for adding more grenades through configs.
Added class MavicDropConfig and array allowed_grenades for allowing grenades for attaching to mavic
Also added variables fake_grenade and normal_grenade in grenade class for grenades with time fuse.

Fixed bug - white smoke seems like hand grenade when attached.

Fixed bug with still attached grenades after drop.