enable API version 6.0 for Get-VSTeamUserEntitlement

[mnieto]

PR Summary

Allows to take advantage of the filter parameter defined in the API v6.0 Defines a new parameterset specific for v6.0 onwards, and ensure that the existing top and skip parameters only can be executed with lower API versions

Fix #388

PR Checklist

• [x] Write Help
• [x] Write Unit Test
• [x] Update CHANGELOG.md

[mnieto]

@SebastianSchuetze , I sent my comments regarding to the _countParameters function. What direction should I get?