Suggest making class-based resources re-use module DscResource.Base

[johlju]

The class ResourceBase and Reason, plus enum Ensure have been moved to the module DscResource.Base so that we don't need to duplicate code between DSC resource modules.

Suggest that the class-based resources in thi module re-use that module by modifying RequiredModules.ps1 and build.yaml to use it the same way we re-use commands from module DscResource.Common.

This move has already been done for SqlServerDsc, and I have tested so that the resources from different modules do not clash when re-using the module DscResource.Base. I documented it here: dsccommunity/SqlServerDsc#1790