Use packaging.version.Version to sort filenames by the version of the package they represent. Alternate implementation of that proposed in #829. Also ref #629.

Add test to verify the install of Pypi top packages

Add a namespace module.

Remove _add_defaults_data_files override

Fix spacing after comment hash.

Fix quantity of blank lines.

Fix spacing after comment hash.

Fix quantity of blank lines.

Sort manifest file list in tests

Different OS's and file systems return lists of files in different
orders, not always creation order. This caused intermittent test
failures.

The file list is now sorted prior to being checked to ensure a
consistent order across all systems.

Fixes #816