Maven root universe

The provided code does the following:
* Introduces a new operation which takes a file system path and recurses the path and all its sub directories, adding all found maven projects to the universe (a so called 'maven root universe')
* Introduces a respecting command `projectRoot <path>` in the CLI
* Introduces a new universe selection in the Eclipse dialog which -- on selection -- opens a directory dialog which lets the user choose the desired root folder to be searched.