workflows: new stage for halted

* Adds 'WAITING' stage for halted workflows with
  no action added to them.

 Signed-off-by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>
workflows: New stage for error

* Adds new stage for objects that encountered an error.

Signed-off-by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>
workflows: detailed workflow task list

* Displays workflow definition and completed tasks in details page.

* Task names to display are chosen from the description attributes
  of the task, if not present from the first line of the docstring,
  if still not present, the function name is finally used.

* Adds a decorator to pass the attributes (docstring, name) of a
  function to its closure.

* Adds the decorator to oaiharvest tasks.

Tested-by: Jan Aage Lavik <jan.age.lavik@cern.ch>
Signed-off-by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>
oaiharvest: tasks decorated

* Decorates tasks to pass their attributes to their inner function.

Signed-off-by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>
deposit: tasks decorated

* to pass their properties into their closure.

Signed-off-by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>
workflows: testsuite adapted to new stages

Signed-off-by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>