ACE-502 - Allow import of DPs from other ACE server

- import all new/non-existing artifacts;
- recreate the features and distributions and link them to
  the artifacts as mentioned in the DP;
- added support for fix-packages and ensure that no artifacts
  are missing that are not available in the OBR.



git-svn-id: https://svn.apache.org/repos/asf/ace/trunk@1646482 13f79535-47bb-0310-9956-ffa450edef68