Test host provisioning

* Fix for remove host not waiting until request submitted
* Added remove_host_from_cluster() method to all mgmt_systems
* Added _destroy_host() private method to vsphere to remove host from inventory
* Added support for datafile file_handle passing in setup_customization_template()
* Added new fixture @host_provisioning_setup_data to return the host provisioning data
* Added new page models for HostProvisionRequests
* Added provision button handling in Hosts
* Added click_on_datastores() method to host Detail class
* Added new header menu for Requests
* Added life cycle buttons to Mixin by default
* Added modelling of all the host customization request page
* Added new test_host_provisioning test
* Added data file for customization