Changed some code to work well with my Addon.

Added methods in ItemZeldaShiled
(isMirror, isWooden, isElectricResistant, setMirror, setWooden,
setElectricResistant)
Code not tested.

Added stuff in ZSSItems
(DekuShield.setWooden & MirrorShield.setMirror)

- I'm not sure that it will work.