added boneyard wolf

Added unsupported support for crabs. The intention is that pet crabs can equip the dog backpack, but i can't find a reference to pet crabs in the FCS so i just added crabs to the list of animals that are allowed to equip the backpack. I have not tested it, and the packpack will almost certainly not properly fit on crabs.

Slighty reduced availability in shops to reduce stack size of dog backpacks in shops.

Added goats to the races allowed to use the backpack. Does not properly fit.

Added Beak Thing to the races that are allowed to wear the backpack. Not tested, possibly does not fit properly.

Added Gorillo to the races that are allowed to wear the backpack. Not tested, possibly does not fit properly.

The backpack should now be also be available at travel shops in major cities.

- icon fixed
- reduced encumberance effect to 50%
- removed stealth penalty
- reduced combat stats penalty
- increased stack bonus to 3x
- increased cost