expose domain parameters via the API

Implemented domain parameters in the same style as hostgroup parameters.

Before:
jpoppe@astray98:~/git/foremanbuddy$ ./foremanbuddy.py -d domain info 1
debug: url "http://overlord001.xx.ebuddy.com:3000/api/domains/1"
debug: method "GET"
domain : name       : xx.ebuddy.com
         created_at : 2012-12-27T21:59:48Z
         updated_at : 2012-12-28T09:04:28Z
         dns_id     : 1
         fullname   : xx.ebuddy.com
         id         : 1
jpoppe@astray98:~/git/foremanbuddy$ 

After:
jpoppe@astray98:~/git/foremanbuddy$ ./foremanbuddy.py -d domain info 1
debug: url "http://overlord001.xx.ebuddy.com:3000/api/domains/1"
debug: method "GET"
domain : name       : xx.ebuddy.com
         parameters : new: api, does: rock, in: foreman
         created_at : 2012-12-27T21:59:48Z
         updated_at : 2012-12-28T09:04:28Z
         dns_id     : 1
         fullname   : xx.ebuddy.com
         id         : 1
jpoppe@astray98:~/git/foremanbuddy$