Import process: untie from @gracinet personal bitbucket account

We have this technical requirement of adding me, @gracinet, to the project members, so that it gets listed on the Bitbucket import page.

Obviously this is subpar and doesn't scale. Some ideas:

• make a true Bitbucket account for @bitbucket_importer and share its password with all administrators of foss.heptapod.net
• change to membership by the heptapod_net team, if that's even possible (needs to be tested)
• adapt the import page to replace the filtering based on membership by filtering based on path of public projects. More recent GitLab versions have such a filter, but I think it's on top of the membership. We'd have to add an additional page to give the path before displaying.