Split Kobold out of Shadowdark Core Source

[xanstin]

Currently it shows up as part of the core rulebook when it was a forum created addon not part of any core rulebook.

Split out similar to Bard and Rogue since it was created in a similar fashion.

[PrototypeESBU]

Bard and Ranger are currently under their own tag. Yes, Kobold is a weird one, but I think we can move under the B&R tag similar to how shadowdarklings does it.