aca_common.ps1 is a common place to define all of the paths necessary for deploying the ACA on Windows. This reduces chance of typo errors. It enhances consistency. And simplifies maintenance of paths and keys across all scripts.

Any other script can access these global variables by importing the aca_common.ps1 script.

This issue is to ensure each script is making use of these common paths instead of defining their own. It should also create new global variables for the property keys.