Warn if v5 export Using a v6 Translate File

[emmahodcroft]

Address first part of issue #379 . Possibly less useful, as unlikely may people switch from v6 back to v5. Can take or leave this as we see fit.

Adds a check to export to look for v6-style translate files.

If the AA muts file seems to have been made with v6 augur translate (it has strand values of + or - rather than 0 or 1), then it will modify the provided start number and strand values to match the v5 format.

It also prints a warning to the user saying it looks like the file is from a newer augur version, that we've tried to convert it, but that we recommend them re-running translate and then running export again.

[jameshadfield]

This will require a new release to v5 for people to get these changes right?

[emmahodcroft]

Yes, it would. Which is maybe what makes it questionable? But it would make make sense, as it would protect against this mixing up of v5 and v6.

[jameshadfield]

Just updating this PR with some comments from slack -- there is an appetite for a further v5 release, which this should definitely be part of. (It's also desired to make augur export v1 synonymous with augur export in this v5 release.) I'm in favor of merging.

[trvrb]

I'm in favor of merging. Thanks!