(CFACT-124) Refactor kernel resolver into a base that can be used by Windows.

The base resolver is now responsible for adding the facts.  The POSIX child
type gets the data only.

This will allow us to share the fact definitions between POSIX and Windows.
(maint) Add missing doc comments.

Adding missing doc comments to make doxygen happy.
(CFACT-124) Refactor base DMI resolver so it can be shared by Windows.

Refactoring the base DMI resolver to keep the fact definitions in a
single place (the base).  The child types are only responsible for
returning data to the parent.
(CFACT-124) Refactor filesystem resolver into a base implementation.

Refactoring the filesystem resolver into a base implementation that is
responsible for the fact definition.  Child types are only responsible
for populating the data.