Initial support new messages grouped by severity

As discussed in dev mailing list many months ago.

At this time we have only errors. These errors is a `List` of `Message`s. But some applications needs to messages like warning and info. We have a `Severity` enum with properties like `INFO` and `WARN`, but this messages is not used by VRaptor.

With this pull request we can simple add a `Message` into `Messages` managed bean. So in the view we can use someting like this:

```
<c:forEach items="${messages.errors}" ... />
<c:forEach items="${messages.warn}" ... />
```

Categorized messages are available too: `${messages.warn.from('client.name')}`, and more.

This change has backward compatibility because `messages.errors` is exported to view with alias `errors`, that is the same object. 

This is an initial suggestion, and we can improve it. After, javadocs and site docs will write.

Thank you.
Makes total sense. :+1

On Friday, August 15, 2014, Rodrigo Turini <notifications@github.com> wrote:

> In
> vraptor-core/src/main/java/br/com/caelum/vraptor/validator/Messages.java:
>
> > +/**
> > + * Managed class that stores all application messages like errors, warnings and info. This
> > + * class is useful to display messages categorized by severity in your view. To choose a severity
> > + * you can construct your message like this:
> > + *
> > + * <code>
> > + * 	Message message = new SimpleMessage("name", "An info message", Severity.INFO);
> > + * 	validation.add(message); // will stored as INFO severity
> > + * </code>
> > + *
> > + * @since 4.1
> > + * @author Otávio S Garcia
> > + */
> > +@Named
> > +@RequestScoped
> > +public class Messages {
>
> guys, "messages" is a really generic name, it is causing some problems
> at our internal projects (there is a lot of "messages" vars included to
> JSP)
> What about change it to "VRaptorMessages" or something? It'll help a lot
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/caelum/vraptor4/pull/736/files#r16295214>.
>