TMSS-761: added readonly property SAPs which returns a QuerySet containing all SAPs of the subtask's output dataproducts

Bug Fixed

TMSS-703: Cancel running obs on triggered obs, add project property to subtask, modify path_to_project to deal with ManyToMany fields

TMSS-725: processed review comment: split the ERROR state into (generic)ERROR and UNSCHEDULABLE which are both end-states.

TMSS-725: fixed tests, and added convenience method to set a subtask to a desired state following the allowed transitions.

TMSS-725: added a SubtaskAllowedStateTransitions table, populate it with the allowed state transitions, and raise an exception if a user tries to submit an illegal state transition

Changes updated based on review comments

TMSS-648: removed weird excaped line ending handling. Added prerequisite for is_feedback_complete, the number of output dataproducts needs to be > 0

TMSS-307: while working on TMSS commissioning with TMSS-573 it showed that feedback processing was not robust against undeterministic feedback message order. Now it is.

TMSS-573: Seperated TMSS into sub-packages TMSSBackend, TMSSFrontend, TMSSClient and TMSSServices and used the proper dependencies on using-lofar-packages like QA and SCU where TMSSFrontend is not needed.

TMSS-344: modify models for pinning and test data, add logic for task draft and blueprint creation and test coverage

TMSS-320: added methods to get/compute the progress of a subtask, process_archive_information for a dataproduct, and to find the transformed_output_dataproduct for a given input dataproduct

TMSS-320: replaced FK by OneToOneField because a single dataproduct has a single archive info. renamed related_names. added ADLER32 hashtype

TMSS-320: changed SIPidentifier to make it lighter in storage and (de)serialization. Changed ForeignKey into OneToOneField, ensuring each SIPIdentifier is used only once. Create new SIPidentifier instances where/when needed by default. Adated scheduling of observation/pipeline subtasks for bulk creation and usage of global_identifiers, and added a schedule_ingest_subtask method.

TMSS-190: let stoptime be set by client(s) instead of assuming that a state update to finishing should always set the subtaks's stoptime

TMSS-322: reimplemented this feature. As stated in the ticket: such a convenience log_url is not part of the Subtask model, but can be a view on the model. So, implemeted it in the viewset. Now, fetching subtasks from the TMSS db is superfast again.