fontinfo.plist import/export v4. update for PR 215

see https://github.com/metapolator/metapolator/pull/215
During the call there was also an open discussion of what we should do to merge all these fontinfo.plist files that are imported. There was no consensus then and I do not have any myself. I'm sorry if I haven't been able to answer this on the other occasions you asked, I am open to suggestions for it. It is not a simple issue, I now have some idea of what mutatormath does, but do not magically know the right thing to do.