cloudstack driver

This is a fully working and tested CloudStack driver for docker machine. All info needed to use this driver for your (private) CloudStack setup can be found in the updated README.

Of course there are a lot of use cases (different CloudStack setups) that could need more and/or other options to make the driver also work for those use cases. But since this is not predictable and this is currently tested with standard basic and advanced zones, most use cases should be covered without additional work.

Currently there also is an open WiP PR (#82) for a CloudStack driver, but @dduportal is in the loop and together we decided it was best to make this new PR in favour of the existing one. So @dduportal will contribute to this driver if needed and the PR #82 will be closed.