Fixes #204 - Remove AS from environments page

Merged import facility in Environment and Puppetclass controllers

Fixes #175 - A link is provided to import classes and environments

There is now a link on both the environments and classes page which
imports any new classes or environments into Foreman.

added some basic nested views

Add support for multiple puppet classes per host / operating system / environment etc
this should enable a proper dropdowns when creating the gui part that shows possible puppet class / operating system / env combinations

fix external nodes to actully work with multiple puppet classes...

fixed an issue with wrong contoller names which lead to broken links, redid some model relationships (hopefuly simplified - hence removed the nested_has_many_through plugin

realigned models to use :though and habtm when it made sense, setup basic AS controllers to support that