Appliance set provisioning now asynchronous

Fix region parameter passing to subprocess.call() in Appliance.enable_external_db()

Update - Appliance.patch_ajax_wait() can now pass without triggering exception

Fix - return correct db address for session on non-db appliances

Update docs

Update wait_for_web_ui() - add 'running' parameter, timeout raised to 20sec

Fix - Appliance.name now correctly updated during Appliance.rename()
Merge pull request #479 from jkrocil/appliance-util-async

Appliance util - asynchronous provisioning of appliance set