(*) [CTL-81] Prevent a change in case the validationsummary has not changed which should improve performance in some cases. Note that for this
    to be reliable, Catel uses the Stopwatch instead of DateTime because DateTime is not accurate enough. Since the Stopwatch is only available
    in the full .NET framework, all other target frameworks will always assume a validation context or summary is outdated

This is a change for CTL-95