Changes to the config.yml to support permission based lasso.

Mobs can be leashed only if they are permitted under the lasso.mobs section in the config.yml. Additionally, if the lasso.perms option is set to true, then each mob will be disabled from lasso unless that permission is given to the player or group (i.e. lasso.chicken).

The permissions name names will be similar to the names in the mob list.