Set/Test/Export and other updates for PSAdapter

[anmenaga]

PR Summary

Updates:

1. Added implementation and re-enabled tests for script-based and class-based resources for Set and Test operations
2. Added implementation and re-enabled tests for Export operation (class-based resources only)
3. Fixed regression in custom psmodulepath in configs
4. removed PSDesiredStateConfiguration v2.0.7 module from being shipped in DSC releases
5. removed unneeded Configuration/BaseRegistration files that were left over from 1st iteration of Michael's PR
6. moved everything except resource json manifests into psDscAdapter subfolder

Notes:

1. PSAdapter at this point has a dependency on PSDesiredStateConfiguration module (for both: script-based and class-based resources)