(CFACT-18) Implement EC2 facts.

Implementing the ec2_metadata and ec2_userdata facts in libfacter.

These facts will be resolved when under a kvm/xen hypvervisor and the
BIOS version has "amazon" in it.

The ec2_metadata and ec2_userdata facts match exactly to what is output
in Ruby facter.

As the "flattened" facts from ec2_metadata were marked deprecated in
Ruby facter, we've dropped support for them.
Why not a regex? Way too many solutions are proferred here: http://stackoverflow.com/questions/4654636/how-to-determine-if-a-string-is-a-number-with-c. Alternatively, use boost::lexical_cast<double>, or without throw http://www.boost.org/doc/libs/1_56_0/doc/html/boost_lexical_cast/synopsis.html#boost_lexical_cast.synopsis.try_lexical_convert