Core/Players/DK: Implement Rune Grace Period mechanic

Closes #11736
Fixes #6122
Scripts/Examples: Remove some more code related to example scripts
Core/Spell - Fix Remove Aura "The Eye of Acherus"

Fixed remove aura "The Eye of Acherus" http://www.wowhead.com/spell=51852 after use "Recall Eye of Acherus" http://www.wowhead.com/spell=52694 .
Earlier, after using the player remained under the aura.

Signed-off-by: jackpoz <giacomopoz@gmail.com>