(A.G.) Revision of analysis classes containing following changes:

(A.G.) Revision of analysis classes containing following changes:
   - Removed misleading virtual method AliAnalysisTask::Cleanup()
   - Introduced optional method AliAnalysisTask::FinishTaskOutput() that will be executed on worker nodes in SlaveTerminate() phase, after processing of last event but before the outputs are wrote to files/sent for merging. Output objects should NOT be cleaned-up in this method, but in the task destructor.
   - Output histograms in memory will not be deleted anymore when closing the output file - user have their ownership.
   - AliAnalysisTask::Terminate() called now before the outputs are written to files
   - Experimental feature for CAF: AliAnalysisDataContainer::SetSpecialOutput() can be called to force merging in PROOF via files. In this case calling OpenFile(out_slot) is mandatory in MyTask::CreateOutputObjects()
   - Refined debug level in the framework: level 0 - no verbosity, level 1 - calling sequence, level 2 - more info