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.
Sure, this is the point I want to discuss with you. My goal with pull request is merge both classes. But to avoid break compatibility I think to leave `ServletBasedEnvironment` as deprecated to warn users to migrate to `DefaultEnvironment`. But `DefaultEnvironment` must be `Vetoed` and can't extended. So... what you think to simple drop `ServletBasedEnvironment` and postpone this pull request to next major release?

Or do you have another idea? I'm not sure about the best choice.