Measure Path extn, allow smaller Scale Factor

Migrated from: https://bugs.launchpad.net/inkscape/+bug/1699359

It seems the Scale Factor in Extensions menu > Visualize Path > Measure Path does not allow scale factors below 0.1. You can type in a lower number, but it defaults back to zero.

The use case is measuring Area in acres. There's not a unit of acre available, so the user has to make some calculations to use the Scale Factor, so that the resulting area value actually is acres.

Reference forum thread: https://forum.inkscapecommunity.com/index.php?topic=655.0

Thanks.