Add fix to return enum string values

[Gijsreyn]

PR Summary

This PR addresses #791. While it is a small redesign, casting the value to a string makes logical sense. When users are exporting or getting values, they can capture the results and store them as a configuration document instead of having them returned as integers. This would match the schematics, even though that is not implemented fully.

[Gijsreyn]

@mgreenegit I'm bothering Steve too much, so I thought of giving you a heads-up. Could you take a quick look at this one? It shouldn't be that big of a change.

[Gijsreyn]

Thanks @michaeltlombardi for the check. I thought there was a remark once to do it in the style Pester tests are written (OTBS). I switched the blocks in psDscAdapter.psm1 to match that style.