Unify date/time format and make it cultureInfo independent

[mnieto]

PR Summary

Fix #511
Date format in .github/moduleMessages.json is different than test/sampleFiles/moduleMessages.json
Also the [DateTime]::Parse can throw execption depending on the current locale.

This change unifies the date format in _showModuleLoadingMessages function using ParseExact instead Parse

The field toDate in moduleMessages.json should have dd/MM/yyyy HH:mm:ss format

PR Checklist

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

[SebastianSchuetze]

Thanks for the fix!