Adding support for alias when validates the bean.

This pull request closes #826.

As discussed before, I added new methods adding an alias parameter. If alias is not null, the value will be prepended to the category. We need this because using method validation we can discover the parameter name, that is added to category. But using manual validation via `Validate.validate` we isn't able to discovery this name.

Note: this pull request adds new methods in `Validator` interface, so can break apps that implements this interface but don't inherits `DefaultValidator`. So may we can wait a new minor release like 4.2.
I prefer the `if` :)