Register QLayout as uncreatable type for SizeConstraint enum
Add support for <set> properties of UI files
Add font property handling
Allow element "name" attributes to be empty

Some UI files seem to miss the "name" attribute for elements such as
layouts.
Since the name is not strictly required in QML anyway, just warn when
name is present but empty.
Fixed spacer policy enum writing
Enable ui node visitors to register QML imports
Fix font weight handling

QML Font enum needs QtQuick import
Change object's name when id generation finds a duplicate
Store object name -> id mapping in shared visitor context
QmlWriter cleanup
Add support for connection element

Write QML Connections {} elements into top level (first) widget.
Signal/Slot connections with arguments need some manual adjusting,
generate TODO comments with hints.
Add layout contents margins
Add support for layout contents margins to ui converter