Fixes and improvements
- Fix legend showing wrong symbol for layer sub items with same name and fix insertion of rows with pre-existing children
- Fix double feature creation when adding points in fast editing mode
- Fix snapping to segment
- Always show the cancel/delete button in the add feature form
- When exiting the multi selection mode via the back key, clear selection
- Avoid loosing the focus (asking to close on back key)
- More feature form improvements (adjustment on date editor etc.)
- Relation reference combo box fixes and improvements
- Improvements to the checkbox editor widget
- Fix feature form problems on using conditional visibility