Add a Windows network state

This pull request does the following:

1. Adds a state module for management of network interfaces.
2. Enhances the ``win_network`` execution module to support multiple IP addresses on a single interface, and adds several new functions.
3. Moves the ``find_changes`` function from the ``pkg_resource`` execution module to within ``salt.utils``, allowing it to be used to compare changes to the network interface configuration. (refs from the pkg providers have also been updated to reflect this).