updated fontinfo.plist support

This is just a start. In this we import just the first fontinfo.plist that we see when bringing in the masters from UFO files.

After this we will need to work out what we are planning to do with this information during an export.

This is inline with the updated spec at https://github.com/metapolator/metapolator/issues/295
And since it is so different, replaces the older code at https://github.com/metapolator/metapolator/pull/293