removed the special treatment of NotEmptyValidation

src/main/java/ninja/javafx/smartcsv/validation/Validation.java

@@ -33,4 +33,5 @@ public interface Validation {
     enum Type { NOT_EMPTY, UNIQUE, DOUBLE, INTEGER, MIN_LENGTH, MAX_LENGTH, DATE, ALPHANUMERIC, REGEXP, VALUE_OF, GROOVY }
     void check(int row, String value, ValidationError error);
     Type getType();
+    boolean canBeChecked(String value);
 }