We need a widget for entering/editing quantity values. As a start, this could simply accept a string and leave all validation to the backend. Eventually, we'd want to be able to enter the "main" value, upper- and lower bound (or an error margin). A preview could be added similar to the one used for geo-coordinates.

Once we support unit conversion, we'll also need to be able to enter a unit of measurement.

Version: unspecified
Severity: major