Used weapon_* entity intead of weapon_*_spawn for the items dropped.

- Destroy every gift dropped by this script upon map restart.
- Added glow settings.

jun, u stupid, stop making typos.

oops

- the drop chance is now independent from the convar, use the ems setting to change it.
- added configurable settings.
- opening the gift now emits gift_pickup.wav instead of littlereward.wav.