Funtoo

This removes the funtoo-latest-generic_64-stable template and renames funtoo-latest-x86_64 to funtoo-stable-x86_64 . 
The funtoo-unstable-x86_64 template is derived from funtoo-stable-x86_64, mostly changes to ACCEPT_KEYWORDS and the default ruby version.  Puppet versions <=3.3.2 requires a patch to work with ruby2.1.  The puppet upstream has already fixed this https://tickets.puppetlabs.com/browse/PUP-1243. 

I removed rbenv in favor of native ruby packages and then using 'gem install' to install gems.

I tested both with validate and they pass.
597M  funtoo-stable-x86_64.box
701M  funtoo-unstable-x86_64.box