don't remove prj meta when freezing

- Preserve title and description of the frozen prj (issue 1585)
- add a small stagingapi wrapper for makeurl, makes the code easier to read
  - url = makeurl(self.apiurl, ...
  + url = self.makeurl(...
- don't freeze AGGR (issue 1611)
Merge pull request #55 from openSUSE/coolo_1585

Looks good