Added informative @Nullable annotations to Validation.
Javadocs for Validation.
Javadocs for ValidationMessage.
Javadocs for Validator interface.
Javadocs for ValidationHandler interfaces.
Javadocs for RequiredValidator.
Javadocs for EmailValidator.
Javadocs for ReadFormatter.
Javadocs for Formatter.
Javadocs for ProvidesValue.
Javadocs for PropertyAccessor.
Removed unecessary classes.