(PUP-1066) Add the ability to delete files.

Add a .destory and .destroy? in order to flag files for deletion.
We also sneak in a .entries reader in order to let us read the
entries directly.

This should fix PUP-1066 and #12687.
Initial refactoring of yumrepo.

This work strips out all of the provider code from the type, and
creates a new ruby provider for yumrepo.

While this code still uses inifile it's been rewritten to take advantage
of the modernization of Puppet.  It's now a little easier to understand
and test.