Several enhancements to datastore support for the SCVMM integration

1)	Extended datastore support to include a datastore object for the local storage on the hyperv box. Explicitly filtered out "System Reserved" volume in the powershell script since we will not provision there.
	There were several ways to gather both local and shared storage; the simplest yet most economical way was to change the powershell script to gather the disk volumes in the get_host() function while we are gathering the host objects, this avoids making an extra powershell call.
2)	Changed the VM location property to be the location of the VMC file ( vm config file) minus the drive.
3)	Changed the datastore name to be a URI and to include the hostname in addition to the volume name.

FYI - 2) and 3) above will be concatenated to enable fleecing.

All of the above changes involved modifications to the spec tests and generated data files.
Replaced the method drive_letter_regex with a const
Merge pull request #23 from bronaghs/scvmm_datastore_enhancements

Several enhancements to datastore support for the SCVMM integration