refactor standalone distribution assembly

I refactored the assembly descriptor of the standalone distribution. The motivation for this was that the setup with <moduleSets> works only when you're building the whole project. So you can't just quickly rebuild only the distro if you're working on it. So I started moving everything to <dependencySets> and done couple more refactorings. In the end we have much more concise assembly descriptor (500 lines to 100 lines), that should be easier to maintain in the future and can be built separately. The only difference is that now jars in the lib directory have full qualified names with versions, but IMHO that's the good thing as users can easily see what version on the lib they are using (if necessary).