LOGBACK-700 + ImportCustomizer for GafferConfigurator

Added jmxConfigurator method to ConfigurationDelegate which allows overriding the default context name or the entire ObjectName

 The customizer auto-imports commonly used types, packages and Level constants (incl. their lower-cased names as aliases)

Fix for LOGBACK-782: Syslog suffixPattern property cant start with a character in range [a-zA-Z0-9]

Fix for issue LOGBACK-782 with test. The fix consists of forcing the nopex variable to be defined with no arguments, so the parser wont get confused and try parsing the variable concatenated with the next string