Minor bug fixes and typos

Mostly fixes for various typos and grammatical errors, but also has a few small bug fixes:

-"of mastery" and "of perfection" amulets now check for conflicts between amulet power source and the category boosted

-Dwarf's Stone Walking racial is no longer usable to target an empty space and move one tile

-Added a long_desc to the stun effect noggin knocker gives to prevent an error when the player is hit by it