Add QueueAdapter objects inspired to fireworks + Replace RunMode with TaskManager
 Replace isinstance with duck-type testing
 Code cleanup
 Minor modifications.
 Minor changes.
 Complete interface of QueueAdapters.
 Workaround in workflow.connect()
 Change extension uses for ABINIT stderr files.
 Make FloatWitUnit and ArrayWithUnit compatible with pickle
 Sketching the interface for the automatic parallelization with ABINIT
Merge remote-tracking branch 'mpmaster/master'
Merge remote-tracking branch 'gmatteo/master'