Stopping streaming on file plugins discards all arrays in queue

[MarkRivers]

If a file plugin is in streaming mode then when streaming is stopped (setting Capture=0) any NDArrays currently in the queue will be discarded. I don't believe this is the desired behavior.

Example:

• User is viewing camera images collecting at 100 frames/s in a viewer which can keep up with the image rate.
• HDF5 file writer is streaming data to disk, which cannot keep up at 100 frames/s. User has set a large queue to buffer images because of this.
• User sees the end of the interesting action, and stops the HDF5 file plugin, expecting that it will save all frames up until the time when the file plugin was stopped.
• This is not what happens, in fact all frames in the queue are discarded, and some of the interesting action has been lost.

I think setting Capture=0 should not immediately close the file, it should first empty the queue and then close the file.