Ignore more meta-commands

[rdunklau]

I'm not sure this will be accepted because it can modify the behaviour.
However, in certain cases, in can be useful to have those meta-commands in the SQL file and handle them when running the files manually, and drop them if the files are run through django-north.

[k4nar]

Ideally it would be great if we could execute those instructions instead, to make sure we run the actual DML.

Also we should fix this in https://github.com/peopledoc/septentrion/ instead, as soon django-north will just be a wrapper around it.

[ewjoachim]

I second @k4nar ’s comment.

If I understand correctly, those instructions are understood by psql, so this would mean quite the shift in the way it works: either we’d need to parse them ourselves or we’d need to shift from psycopg2 to psql subprocess.

That being said, it would probably work.

@rdunklau would you mind opening a septentrion issue ? Or I’ll do it.

[ewjoachim]

Ok, I think we'll go the way of peopledoc/septentrion#73

If it's ok with you, @rdunklau, I'll let you close the PR.

Thanks for the contribution though, it's highly appreciated, and started a discussion that will end up improving both projects !