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
@muktaa, thoughts on this? I assume this is the up to date doc on parameter sets: http://msdn.microsoft.com/en-us/library/dd878348(v=vs.85).aspx.