Change vdc name method names for consistency

`vdc_name` becomes `vdc_1_name`.
`vdc_name_2` becomes `vdc_2_name`.
Change input parameter names

Change the names requested from the config file for vdc names, for consistency. E.g. `vdc_1_name` instead of `vdc_name_1`.
Rename catalog_item as vapp_template

For some reason it has been called `catalog_item` in all our configuration code, but in vCloud Director it is called a vApp Template. This renames the testing code to use the correct name. There is an outstanding story to change the actual configuration code as well: https://www.pivotaltracker.com/story/show/70452106.