Do not embed/wrap 3rd-party bundles in our sources

in devstudio/extras, we can see that we define some "wrapper" bundles for 3rd party deps (findbugs, pmd, spring...). This is not the most straightforward approach, and it seems like we could improve it. Here are some reasons that would have justified this implementation, and some reasons why we can improve it:

> a) the plugin and feature have the same IU name and therefore confuse Tycho
How is this possible? p2 adds .feature.group to features. We should think about a 3rd-party feature that requires either this plugins or features, that we could provide in the extras site.

> b) the plugin contributes to the welcome screen and breaks JBDS, so we override that
According to Max, this is no more the case.

> c) because the license doc is incomplete so we provide a more explicit/accurate license by wrapping it w/ our own feature
We can use our feature and add this bundle as required, so we use their bundles and they are installed from our feature. Using required allows people to perform updates from the other sites by themselves.