[sd2_mr0672] Restore sd2 Gundrak version except mr improvements.
[sd2_mr0673] Use auto-registered script for "at_hot_on_the_trail" areatrigger.
[2850] Add achievement support for Assembly of Iron and the Four Horsemen

This will also implement achievement: And They Would All Go Down Together

Conflicts:
	scripts/northrend/ulduar/ulduar/assembly_of_iron.cpp
	sd2_revision_nr.h
[2880] Allow Sapphiron to be spawned using GO 181356

This expects CMangos [12463]

Conflicts:
	sd2_revision_nr.h
[sd2_mr0674] Improvements in Naxxramas