Bundletree improvements

Bundle improvements:
* Better Javadoc in some methods.
* Better code encapsulation.
* Bug solved: fill `visitedBundles` Set to avoid cycles in `bundleDependsOnBundle*()` methods.
* Bundle dependency chain issue solved using `refreshBundles()` utility, as exposed [here](https://mail.osgi.org/pipermail/osgi-dev/2014-June/004459.html).
* `javax.inject` dependency added.
* SLF4J binding conflict solved excluding Karaf client, following [Apache Karaf iTests](https://github.com/apache/karaf/blob/master/itests/pom.xml#L50) as guide.