Rename master to main

[dvalters]

Done now, moved branch master to main with

git branch -m master main

git push -u origin main (or whatver your origin remote equivalent is called. (Don't accidentally get it mixed up with the gitlab remote like me...)

Updated the default branch in settings.

Changed target branch of current pull requests to main.

There are some refernces to master in versioneer.py but I think these are from the versioneer code itself, or refer to other repos, so I left them in(?)

Probably just needs a once over check from @volcan01010 or someone to confirm

[dvalters]

Done now

[metazool]

<3