workflows: task result upgrade

• NOTE Adds an update script to change any existing task results from being an WorkflowsTaskResult instance to a dict.

• Removes WorkflowsTaskResult class.

• Changes task results to no longer be grouped by last_task_name in order to support adding task results outside of workflows tasks.

• Updates documentation with new information on task results as well as actions, workers, extra_data.

• Renames actions API function add_action() to set_action() to better describe what the function does.

• Adds a test case for this new functionality.

• Factors out a function in utils to get rendered task results from the blueprint.

• Changes the fulltext route to a better schema using send_from_directory to avoid exposing any file on the system to logged in users.

• Updates location and task result of saved files in task fulltext_download().

• Simplifies the "heavy" workflow definitions a bit as well as the output of the generic harvesting workflows.

Reviewed-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>