Make NumericValidator locale-independent

[eugeneRover]

NumericValidator now offers single constructor - NumericValidator(String attribute), and contains hardcoded locale-dependent NumberFormat

It would be great to get a possibility to specify custom number format in constructor, like this:

    public NumericValidator(String attribute, NumberFormat numberFormat){
         this.attribute = attribute;
         this.numberFormat = numberFormat ;
    }

and make old constuctor behave the same way, to keep backward compatibility :

    public NumericValidator(String attribute){
         this (attribute, NumberFormat.getInstance());
    }

[ipolevoy]

@eugeneRover this is completed.