[z2101] Refactor code around SMSG_PLAY_SPELL_VISUAL, drop dead code from Spell

(based on commit [12145] - c2440aa)

(based on commit [s1720] - cf3f01e)
Fixup script_command documentation. Thanks to crackm for pointing

(based on commit 6be541c)

Signed-off-by: Xfurry <xfurry@scriptdev2.com>

(based on commit 5eabc7e)

Signed-off-by: Xfurry <xfurry@scriptdev2.com>