Add batch json output and chunked inference

[StefanFabian]

This also fixes #24
Main changes are:

• Introduction of an option --batch_json_output to output the full result information, including frame scores, when using batch mode.
• Chunked loading and processing of the video.
  This enables processing of longer videos, which would otherwise cause out-of-memory errors.
  A new option --chunk_size_frames is added to allow users to set a value that can fit in their GPU memory.

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