Set default value for the 'use_create_frame' argument to a data sources' start_stream() method to False, making the use of create_frames() the default

[rskew]

Motivation: For writing tests, its useful to have the stream stop once the frames have been processed, so the test code doesn't have to manually stop the stream.
When a data source uses create_frames() this happens nicely, as create_frames() stops the stream once all frames have been generated.
However, when we have a test that processes a single file, the default of use_create_frame=True causes DataSchemeFile to call create_frame() and then not stop the stream.

[geekscape]

There has been a long outstanding need to generally provide an out-of-the-box means of terminating Agents(Pipelines) processes in circumstances other than only CI tests …

• Developer working on their Agent(Pipeline) and wanting that process to terminate once the single Stream stops
• Same deal … but, when testing outside of … or within CI (your goal)
• Production use-case, e.g a Highlighter Agent running a single Task and terminating once complete … equivalent to an Aiko Services Pipeline running a single Stream and terminating
  … those three cases above should be supported (easily out-of-the-box) regardless of the number of frames for that Stream … it could be one frame (File) (as in PR#49) or many frames (Files)

My preference is that the PR#49 suggestion shouldn’t conflict with an Agent(Pipeline), which is very long running and is processing lots of Tasks(Streams) each consisting of a single File(Frame) and not having the unnecessary overhead of starting and stopping a background thread for every Task(Stream) in that case. This use-case was the original motivation for the use_create_frame default of True (optimal performance).

[rskew]

Thanks @geekscape , sounds like I'll leave it with you