Ui improvements

see https://github.com/theforeman/staypuft/wiki/UI-Parameters-for-new-wizard
cc @sseago 
**NOT READY**
We still want an explicit association for layout, but *which* layout to set is determined by the two params (one with the layout names for HA vs. non-HA) and the other with the 'networking' selection (referencing the 'networking' attribute on the layout). Since layouts are uniquely defined by a (name, networking) tuple, these two params together determine the layout. We can't just deal with layout by lazy interpolation like we do with the rest of this, though, since it's not just puppet params that are affected -- we actually create the hostgroups that correspond with the roles associated with the selected layout. I'll try to get a commit that fixes this in this branch later today, but we will need to re-enable the explicit @deployment.update_hostgroup_list method