Merging ServletBasedEnvironment with DefaultEnvironment

As described in #811.

VRaptor was designed to works with Servlet environment, so there is no reason to `DefaultEnvironment` lives without `ServletBasedEnvironment`. Almost all tests inside `DefaultEnvironmentTest` is duplicated in `ServletBasedEnvironmentTest` too.

So with this pull request I merged both classes, and did a some refactor to make some improvements like loading properties file without recreating unnecessary instances. All instances creation are moved to `PostConstruct` method, and more.
> But if an application inherits this class, it will annotated with 
`@Specializes` or another stereotype like `@Component`? 

yes (sorry my delay to answer) 

> So CDI will load this class, or not?

It won't load the class (even adding `@Specializes`). The only way 
to do that would be adding the alternative declaration at the user's 
`beans.xml` file or providing a `priority` here. What about changing to:

```java
@Specializes @ApplicationScoped @Named("environment")
// javadoc with @deprecated warning about it
class ServletBasedEnvironment extends DefaultEnvironment {
   // delegate constructor
}
```