[feature] modified validateKnowRows of MetadataValidator trait to check for PermitEmpty global directive
[feature] added new global directive PermitEmpty to allow empty CSV files
[feature] added new permitEmptyDirective to global directives definition and renumbered parsers
[testsuite] added new tests and modified existing to test application of PermitEmpty global directive under various conditions
[testsuite] added new tests for detection of @permitEmpty global directive