Set the field order when interlace is on

[eisneinechse]

The field order of the interlaced frames is set. This is only a very rude version.
More work needs to be done

[codecov]

Codecov Report

Merging #534 into develop will decrease coverage by 0.60%.
The diff coverage is 0.00%.

@@             Coverage Diff             @@
##           develop     #534      +/-   ##
===========================================
- Coverage    49.37%   48.76%   -0.61%     
===========================================
  Files          129      129              
  Lines        10198    10038     -160     
===========================================
- Hits          5035     4895     -140     
+ Misses        5163     5143      -20     

Impacted Files	Coverage Δ
src/FFmpegWriter.cpp	62.29% <0.00%> (-0.04%)	⬇️
src/Timeline.cpp	38.70% <0.00%> (-2.38%)	⬇️
src/Clip.cpp	39.72% <0.00%> (-0.58%)	⬇️
src/Frame.cpp	47.70% <0.00%> (ø)
include/Clip.h	88.88% <0.00%> (ø)
src/CacheDisk.cpp	71.69% <0.00%> (ø)
src/ZmqLogger.cpp	29.33% <0.00%> (ø)
include/FrameMapper.h	75.00% <0.00%> (ø)
src/Qt/PlayerDemo.cpp	0.00% <0.00%> (ø)
src/Qt/PlayerPrivate.cpp	0.00% <0.00%> (ø)
... and 11 more

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[jonoomph]

LGTM