Install guide instructions for poly lists

[PatrickWeller]

Install guide states: Optional - Load in poly lists (--both_checks flag will bypass the need for two checks on each poly, for dev work only):

python manage.py add_poly_list --list roi/b37_polys.txt --genome 37 --both_checks
python manage.py add_poly_list --list roi/b38_polys.txt --genome 38 --both_checks

Correct commands are now:

python manage.py add_poly_list --list build_37_polys --variants roi/b37_polys.txt --both_checks
python manage.py add_poly_list --list build_38_polys --variants roi/b38_polys.txt --both_checks