fixes #1148 - CRUD on lookup values via the API

fixes #322 Ability to add custom variables and multiple values resovled
in a dynamic Hierarchally order

This commits introduces the ability to define variables per puppet
class.

additionally, each class can have multiple values, depends on the host
which is requesting that variable....

fixes #208 - use nested_attributes for lookup parameters

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"