ChefExtension support in the azure sdk toolkit

Contribution to the Azure SDK Toolkit from Chef - To support ChefExtension cmdlets.
Note - ClogenyTechnologies has a contract with Chef. We have signed the Microsoft CLA. This new PR has been created to accomodate the "rebase" after this repo had been restructured.
Original PR - https://github.com/Azure/azure-sdk-tools/pull/2576
@singhkay , @huangpf 
The case we have is as below:

A or B mandatory
A = ClientRb

B = (X, Y, Z)
X, Y mandatory OR X, Z mandatory
X = ClientServerUrl
Y = OrgName
Z = ValidationClientName