Cisco StackWise Onboarding Feature - LTM

[alhogan]

Closes: #244

What's Changed

• Adds ability to enable onboarding Virtual Chassis
• Adds two new optional entries in the command mapper virtual_chassis and modules
• Initial support for Cisco IOSXE devices that are utilizing StackWise technology

To Do

• Explanation of Change(s)
• Added change log fragment(s) (for more information see the documentation)
• Attached Screenshots, Payload Example
• Unit, Integration Tests
• Documentation Updates (when adding/changing features)
• Outline Remaining Work, Constraints from Design