Extend image_name_template to allow timestamp (Breakthrough#395)

* Added TIMESTAMP_MS to file_path substitutions

* Added $TIMESTAMP to image_name_template in test

* Improved variable name

* Added $TIMECODE to image name template options (also added $FRAME_NUMBER to test)

* Added TIMESTAMP_MS to file_path substitutions

* Added $TIMESTAMP to image_name_template in test

* Improved variable name

* Added $TIMECODE to image name template options (also added $FRAME_NUMBER to test)

* Use semicolon as timestamp separator in filename

* Proper string concatenation

* Updated docstring

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Co-authored-by: Sara Veldhoen <s.veldhoen@beeldengeluid.nl>