[z1952] Implement spell (Decimate)

Thanks to piroy1337 for version of ICC Decimate,
thanks to ZuSe for bumping the issue of missing implementation

Signed-off-by: Schmoozerd <schmoozerd@scriptdev2.com>

(cleaned version of 77ced53)

(based on commit [s1541] - a78c97c)
[z1953] Aura 10848 should not cause UNIT_AURAFLAG_ALIVE_INVISIBLE

Signed-off-by: Schmoozerd <schmoozerd@scriptdev2.com>

(based on commit [s1542] - 1ccc351)