[BUGFIX] Correctly implement validator resolver short notation
Currently, the short notation for validators which has been introduced
with Id807dbfa78ae1388aa8cd53bfc578893eade427c does only support syntax
like TYPO3\FLOW3:EmailAddress; but we should rather support TYPO3.FLOW3:EmailAddress
as this is how we use package keys at all other places which are not PHP code.