fdo#80269 (part): Help button for Calc Form dialog

Add help button in Calc - Data - Form... dialog

Change-Id: I7263fdc8709add1ce9cca69ece20feb14ab71589
Reviewed-on: https://gerrit.libreoffice.org/11204
Reviewed-by: Thomas Arnhold <thomas@arnhold.org>
Tested-by: Thomas Arnhold <thomas@arnhold.org>