Internal improvements for JstlLocalization and unit tests

With this pull request, we lookup `Locale` using a Java 7 method to do this. Some test methods are renamed to a better name.

The `getBundle()` producer have a parameter `Locale` added to allow us to receive a injected object. So we can create an alternative producer if nedded. And using injected `Locale` we avoid method `getLocale()` called twice.
Changed. Thank you.