Fixes #170 - implement usergroups

Added migration
Added tests
Added MVC files
Added the routes as well
Added the program logic and additional views
Added RESTful actions for update and create
Added validations to ensure that usergroup.name and user.login do not collide...

family id can not be forced at this time, as it breaks many fact import operatings, fixing broken tests

fixes broken testfixtures/lookup_keys.yml

fixes #141 - add support to extlookup kind of queries through foreman
usage:
wget -q -O - "http://foreman/lookup?key=ntpserver&order[]=my.domain&order[]=common"
if you want it in YAML, just add:
wget -q -O - "http://foreman/lookup?key=ntpserver&order[]=my.domain&order[]=common&format=yml"