Connect RepositoryManagerDriver with Configuration from common, and finish implementing.

- Connect RepositoryManagerDriver with Configuration (from common) so we can configure the repo-manager's base url (for formatting repository URLs)
- Create a new exception type in the repository-manager SPI section to deal with errors that happen in the RepositoryManager, then ripple those up through the layers.
- Add UrlUtils to help concatenating url parts together...added to common. 
- Add ctor to Configuration to enable slimmer unit tests, then do the same with RepositoryManagerDriver, so we don't have to use weld-se or Arq for simple unit tests.
- Refactor inter-module dependency declarations so all modules have a managed dep at the top level and we can keep project.version expressions out of the poms.
- Add some javadocs to the RepositoryManagerDriver