Added descriptions to wizard spells.

Beefed up Mind Transfer. Can now swap with traitors/revs/etc. Limited to humans and monkeys, and may not transfer to changelings, wizards, or cultists. Targets must still have a mind and a client for this to work (must also be alive).
Mind Transfer now correctly works for mime targets or other targets with special verbs.
Added a proper spell book for wizards.
Changelings are now properly assigned their special role at round start.

git-svn-id: http://tgstation13.googlecode.com/svn/trunk@810 316c924e-a436-60f5-8080-3fe189b3f50e

code/defines/obj/weapon.dm

@@ -985,6 +985,17 @@ Total SMES charging rate should not exceed total power generation rate, or an ov
 	throw_range = 20
 	m_amt = 100
 
+/obj/item/weapon/spellbook
+	name = "Spell Book"
+	icon = 'library.dmi'
+	icon_state ="book"
+	throw_speed = 1
+	throw_range = 5
+	w_class = 1.0
+	flags = FPRINT | TABLEPASS
+	var/uses = 4.0
+	var/temp = null
+
 /obj/item/weapon/staff
 	name = "wizards staff"
 	icon = 'wizard.dmi'