[s1980] Implement Refer-A-Friend System. Thanks all Authors
Taken from
- https://github.com/mangos-one/server-old/commit/00cb8bb4fa9c90e19f612a28f18ad41887f97ee4
- https://github.com/mangos-one/server-old/commit/6a37d17f757075739ec901e222e96fb65bbd6adb

Signed-off-by: Salja <salja2012@hotmail.de>