New -polymorph function

[Amphioxus]

Give imps and non-totem druids a -polymorph function that allows them to take the shape of any small or medium animal as per the imp's Beast Shape I ability and the druid's Wild Shape ability (which emulates Beast Shape I, at least at low levels).

They should be able to take the form of any small or medium sized animal, which includes the following in NWN (leaving off Dire variants):

• Black bear M
• Boar M
• Black/gold/hybrid Cormyrian cobra / Great cobra / Spitting cobra (just "snake"?) M
• Cougar / Crag cat M
• Cow* M
• Deer M
• Dog* M
• Falcon S
• Horse* M
• Jaguar M
• Leopard M
• Lion M
• Ox* M
• Panther M
• White stag M
• Wolf M

I would envision the command as working by typing "-polymorph lion" and turning into a lion. I think it would be great if these were simple appearance changes and not actual polymorph effects, so that they don't blare the "I'm polymorphed!" effect on every transition and don't wear off in the middle of trying to spy on someone. Spellcasting could be disabled while polymorphed in this way, if needed for balance and thematics.

Not all of the creatures on the list would work well with the theme in my opinion, but it would be great to be able to turn into at least a couple of basic types. As an imp character, personally, fey seems to be the only shape worth even trying to disguise as, but it suffers from the OOC declaration of being polymorphed on every transition.

In the PnP rules, imps and druids (at least at low level) can't turn into tiny animals, but it seems to me like there are some interesting ones on the list there too:

• Badger T
• Bat T
• Chicken* T
• Parrot T
• Penguin T
• Rat T
• Raven T
• Seagull T

Particularly badger, bat, rat, and raven would be useful in some cases and fit the theme.