(QENG-1146) Add vagrant_fusion, vmware_workstation, and vagrant_virtualbox providers

Currently the vagrant hypervisor provider just does virtualbox. This
allows the vagrant vmware_fusion and vmware_workstation plugins to be
used instead.
Merge pull request #271 from hunner/add_fusion

(QENG-1146) Add vagrant_fusion, vagrant_workstation and vagrant_virtualbox providers