Output Frame Rate on Concat Operation

The frame rate of the output video from the concat operation is actually set to the frame rate of the first video. Concatenating a themed slide at the beginning, result a whole output video has the same frame rate as the slide video (e.g. 5 frames per second). So the theming operation may end up with frames loss/duplication.

I will implement an optional 'output-framerate' parameter on the concat WOH, so you can set a fixed frame rate or parse the value from the given concatenated video (part-X). The syntax will be like 'output-resolution' (see https://docs.opencast.org/develop/admin/workflowoperationhandlers/concat-woh/) but the new parameter should be optional. Without any settings the processing will be still same.