First version of nova_hyper_v to align with stackforge/puppet-nova

This is the first pull request that contains the base of the refactoring of `nova_hyper_v`. It tries to get as much as possible from `stackforge/puppet-nova`.

It needs more polishing but the core functionality is implemented. Relevant updates:
* New `NovacomputeService.py` less complex (my plan is to convert it in a template an reuse it for different services). It only adds a new requirement on `psutil` to properly stop the service and kill the process.
* Install directly from repository url. `pip` is able to install a package from its URL in the form:  `git+https://github.com/openstack/nova`. This is flexible as each deployment can chose its own repository. Also, if you find this option ok, we can remove the pip dependencies as it should be triggered automatically as dependencies.
* The module is able to configure user/pass of the service.

This requires other PR to be merged:
https://github.com/openstack-hyper-v/puppet-windows_python/pull/6
https://github.com/openstack-hyper-v/puppet-windows_python/pull/5
https://github.com/openstack-hyper-v/puppet-windows_python/pull/4
https://github.com/openstack-hyper-v/puppet-windows_common/pull/11