shift the migrant flag from metadata to the flags column

[bhaller]

fix #666, shift the migrant flag from metadata to the flags column

[codecov]

Codecov Report

❌ Patch coverage is 55.55556% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.80%. Comparing base (98ed022) to head (04f4051).

Files with missing lines	Patch %	Lines
core/species.cpp	55.55%	8 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           multitrait     #668   +/-   ##
===========================================
  Coverage       76.80%   76.80%           
===========================================
  Files             117      117           
  Lines           78760    78763    +3     
  Branches        14296    14301    +5     
===========================================
+ Hits            60491    60496    +5     
+ Misses          18269    18267    -2     

Files with missing lines	Coverage Δ
core/slim_globals.cpp	69.25% <ø> (ø)
core/slim_globals.h	57.89% <ø> (ø)
core/species.h	91.80% <ø> (ø)
core/species.cpp	64.82% <55.55%> (-0.02%)	⬇️

... and 7 files with indirect coverage changes

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[petrelharp]

LGTM! I'll have a look at the python tests next.

[petrelharp]

So far I'm pretty sure the test errors are because the individual metadata isn't getting written out correctly. Trying to figure out how to verify that.

[petrelharp]

here the number of bytes changed, but it didn't change in the schema

[bhaller]

OK, good to go! Thanks for the review, and for finding that bug!