Fix a couple of bugs; add source observation to cluster-observation
Configuration_Link.save split up to saveData and saveUI

- no parameter type
- Reason was, because saveData has a little bit other
  handling of data as saveUI
- from now on, the client will handle the hash generation
  instead of the server (md5 hash using JSON-representation
  of the data to save)
- Configuration_Link.php: write function from now on only
  saves given content and filename to ObjectCache
  (filename = hash)
- add support for serviceUrl parameter for saveData and saveUI