(FACT-65) Extract Resolvable and Suitable mixins

The Facter::Util::Resolution class contained behavior for determining if
a resolution was suitable, the precedence of the resolution, code for
safely resolving values, and code for actually resolving information.
This commit breaks up the Resolution class into a Suitable mixin for
determining if a resolution can run and the precedence of that
resolution, and a Resolvable mixin for handling behavior around the
resolution of a given fact.
(maint) Remove normalization tests from resolvable
Merge pull request #611 from adrienthebo/feature/facter-2/fact-238-extract-resolution-mixins

Feature/facter 2/fact 238 extract resolution mixins