Add support for Azure Stack

[yatna]

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1. Current Status - Some features like Create New Web App, Create New App (Advanced) don't work.

2. Approach - The problem arises mainly because Azure Stack doesn't support the same API version of dependencies. We plan to dynamically load the correct library versions depending on environment. Here the steps -

Install all required versions eg.

"azure-arm-storage": "npm:azure-arm-storage@^x.x.x",
"azure-arm-storage3": "npm:azure-arm-storage@^3.0.0",

Determine the environment by looking at the settings.json Use the correct version of library dynamically using if...else... in all files.

3. Maintenance - We only load a different library when the environment is Azure Stack, so functionality for Azure won't be affected in any way. If the version AzureStack supports changes, we only need to update the package.json file.

[ejizba]

Related discussion here: https://github.com/microsoft/vscode-azurefunctions/issues/2259