help text for range filters

[MortenHofft]

A help text for how to use the range filters would be useful. It used to be there, but seem to have been lost somehow along the way.

Options could be

• showing the help text if no filters are selected (or a special text if not the about text)
• have the place holder text be more explicit
  • this will probably be too long a text
• have a popup/hover when the field is selected.