Resolve TMSS-206

Closes TMSS-206

See merge request ro/lofar!158

TMSS-206: moved successor/predecessor urls from registered urls and viewsets.SubtaskNestedViewSet to the viewsets.SubtaskViewSet with action and swagger_auto_schema, so the API is documented, and we have the actions available in the REST UI

TMSS-206: added get_subtask_predecessors and get_subtask_successors in tmss_http_rest_client.py and provided bin scripts

TMSS-206: added easy to use properties successors and predecessors to SubTaks, and expose them via nested urls

Resolve TMSS-176

Closes TMSS-176

See merge request ro/lofar!157

TMSS-206: added skeleton for tmss_subtask_scheduling_service. Need to implement TMSSSubTaskSchedulingEventMessageHandler.onSubTaskFinished

Fixes for ReST API

Closes TMSS-177

See merge request ro/lofar!153

TMSS-61: add tests and some bugfixing

Closes TMSS-61

See merge request ro/lofar!152

TMSS-61: added some default DataproductSpecificationsTemplate and DataproductFeedbackTemplate. Schema's need to be filled in later.

Resolve TMSS-60 and TMSS-171 and TMSS-198

Closes TMSS-60

See merge request ro/lofar!154