Resource type defaults cleanup

This is again done to make support for hiera easier.
The way we were handling lookup of resource defaults
was over-complicated.

This does a decent bit of cleanup overall, but primarily
focused on resource type defaults and how they get
set during compilation.

Signed-off-by: Luke Kanies <luke@puppetlabs.com>
Reviewed-by: Nick Lewis <nick@puppetlabs.com>