Added 'list_all_vms.py' script

Added script 'list_all_vms.py' which can be used to list all Virtual Machines that contain snapshots.
Script modifications

Made several script modifications for more security and cleaner output. Details as follows:

list_all_vms.py:
- Added snarky remarks (aka comments)
- Modified argument parsing
 - Server and username arguments are now mandatory
 - Password argument is no optional, will be asked if omitted on the cmd line
- Added verbose argument
- Printing data center name(s) only when verbose is set
- Disabled warnings about self-signed certificate during connect

list_vms_with_snapshots.py:
- Added snarky remarks (aka comments)
- Modified argument parsing
 - Server and username arguments are now mandatory
 - Password argument is no optional, will be asked if omitted on the cmd line
- Added verbose argument
- Printing data center name(s) only when verbose is set
- Changed output format. Now boxed as optimized for fixed width ASCII (for example to send auto-generated via email every n days)
- Disabled warnings about self-signed certificate during connect
Fixed argument parsing

Fixed argument parsing for verbose option. It now works as intended (DC name is only displayed if verbose argument is present. Also option does not require an argument now anymore.