Add support for @separator and @quoted global directives

Works towards resolving and closing issue https://github.com/digital-preservation/csv-validator/issues/44

@separator is now implemented, except that TAB does not take a number of whitespace characters, instead it refers to the unicode character 0x09. @DavidUnderdown the Schema should be updated to reflect that correction too.

@quoted will now be parsed by the parser, but will not be acted on as the underlying OpenCSV library we are using auto-magically handles quoted data. This could be improved in future to make it strict.