Resolve TMSS-985

Closes TMSS-985

See merge request !636

TMSS-1124: added missing TaskTemplateExtendedSerializer for specifications_template of TaskDraftExtendedSerializer

TMSS-1124

Closes TMSS-1124

See merge request !633

TMSS-1124: using first is ok according to !633 (comment 24581)

TMSS-1124: create a subtask_output per task_connector_type of the task, but only with role Correlator or Beamformer because that is what observations produce

TMSS-1124: fetch the subtask's input/output dataproducts and all related properties in one queryset. Major speedup

Make sure outputProc does not hang indefinitely. Allows at most 8 hours of processing in non-real-time mode,but we aren't using that. Also improve the error message if the connection gpuproc<->outputproc is lost.

TMSS-1124: use newly implemented SubtaskInput/Output to filter and connect the correct dataproducts between subtasks