cog train: bring functionality on par with cog predict (#1391)
* train: allow specifying weights path
Signed-off-by: Yorick van Pelt <yorick@yorickvanpelt.nl>
* cog train: add image argument, -o, -e
Signed-off-by: Yorick van Pelt <yorick@yorickvanpelt.nl>
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Signed-off-by: Yorick van Pelt <yorick@yorickvanpelt.nl>