py: more detailed error string in Sack.add_cmdline_package().
py: add _hawkey.Repo.updateinfo_fn getsetter.
py: add load_updateinfo kwarg to _hawkey.Sack.load_yum_repo.
Add update object.
Add updatelist object.
Add updateref object.
Add updatereflist object.
Add hy_package_get_updates method.
api change: deprecate hy_package_get_update_*.
tests: add tests for update object.
tests: add tests for updateref object.
py: add _hawkey.UpdateRef type.
py: add _hawkey.Update type.
py: add _hawkey.Package.updates_*_evr methods.
tests: py: add tests for _hawkey.Update type.
tests: py: add tests for _hawkey.UpdateRef type.