support double value validation

src/main/resources/ninja/javafx/smartcsv/fx/smartcsv.properties

@@ -12,6 +12,7 @@ title.validation.errors = Validation Errors:
 # validaton messages
 validation.message.not.empty = should not be empty
 validation.message.integer = should be an integer
+validation.message.double = should be a double
 validation.message.alphanumeric = should be alphanumeric
 validation.message.groovy.exception = groovy script '{0}' throws exception: {1}
 validation.message.groovy.return.null = groovy script '{0}' returns null