Support text and timecode burning through drawtext method in ffmpeg worker, refs: #6582
Support text and timecode burning in transcode action, refs: #6582
Support text and timecode burning in toolbox2-transcode, closes: #6582
Make FFmpegWorker._get_audio_layout_mapping a private method
Use _get_audio_layout_mapping in mux_gxf method in ffmpeg worker
Support minimum audio stream requirements in ffmpeg worker

The new min_stream_lists attribute let the user specifies a list of
minimum audio stream that the output audio layout should honor. If the
input does not have enough input audio streams, empty audio streams are
created.

For example considering that audio_min_streams = (4, 8):
  - if output has 2 audio streams, 2 additional empty streams are
    created.
  - if output has 4 audio streams, no additional streams are
    created.
  - if output has 6 audio streams, 2 additional empty streams are
    created.
Add audio_min_streams option to transcode action
Add audio_min_streams option to toolbox2-transcode
Use _get_audio_layout_mapping in mux_mov method in ffmpeg worker
Do not force audio layout in mux_(flv|mp4|mpegps|mxf) methods in ffmpeg worker
Add audio_channels_per_stream option to transcode action
Add audio_channels_per_stream option to toolbox2-transcode
Add unicode errors ignore to the json parse of ffprobe
Fix the deprecated use of the sgop flag

New versions of FFmpeg do not use any more "sgop"
(since commit a249f0cc23457bc73a249e1b1ca22adcfe5b0894
"mpegvideo_enc: add strict_gop flag to mpv_flags").
It is proposed to used instead "-mpv_flags strict_gop",
which works with a large variety of codecs
(flv encoder, h261 encoder, h263 encoder, mpeg1video, mpeg2video, MPEG4,
msmpeg4v2, msmpeg4v3, etc.)
Fix the generated command when the audio codec is "copy"

The generated an FFmpeg command had "-vcodec copy" instead of "-acodec copy".
added "prores" codec (minimal) support
Replace the Vera font by DejaVu, which is more complete

Keep Vera as a symlink for compatibility (DejaVu is an extension of it).
Add the Liberation and Arial fonts.

Arial is needed for compatibility but it is not Free. Liberation is Free,
metric-compatible and looks very similar to Arial.
So, just provide "Arial" via a symlink to Liberation.
Clarify the License section in the Readme
added support for custom position <x>x<y>