Add script for Tortured Druids/Sentinel in Silithus

* They will now emote and spawn a Hive'Ashi Drone on death (75% chance).
* Tortured druid also had its combat AI added.
All spell IDs are correct.
Timers and threshold for tortured druid are guesswork (probably close to
correct) based on
similar NPCs scripts.

Thanks Metalica for his contribution. Closes #9

Related to Classic DB issue:
https://github.com/classicdb/database/issues/653
Add enrage script to creature 1511 (Enrage Silverback Gorilla)

Related to https://github.com/classicdb/database/issues/629

Sources: https://www.youtube.com/watch?v=cO671tvyeiQ
http://www.wowhead.com/npc=1511#abilities

Signed-off-by: Cala <calaftp@free.fr>
Merge pull request #11 from cala/hive_ashi_drones

Add script for Tortured Druids/Sentinel in Silithus
Merge pull request #12 from cala/enraged_gorillas

Add enrage script to creature 1511 (Enrage Silverback Gorilla)