Warn when partial enumeration values are used

Here's a little known feature that could come back to bite someone later with a broken script:

gsv blah -ea ig

I'm not sure in which version of PowerShell this was added, but you can now use partial enumeration values and as long as that partial value leads to an unambiguous match, it will be accepted.

This may result in errors in scripts that appear to be working correctly if a new emumeration value is added with the same leading characters as those that are in use within a script. It's the same issue/risk with using partial parameter names in scripts. Shorthand should be for ad-hoc use only, and PSScriptAnalyzer should have a rule that warns whenever an enumeration value is used in a script in shorthand (such as in the command above).

Use the example gsv blah -ea ig as the behavior to investigate, and locate the existing PSScriptAnalyzer rule and test structure for comparable warnings. Done means a script using an unambiguous partial enumeration value produces a warning, while full values remain accepted.