`groupbox` widget does not render in Rack

[brylie]

When creating a Rack module with an SVG image widget, the image does not seem to render:

Steps to reproduce

1. create a new Rack module project
2. add an groupbox widget
3. export the plugin
4. load it in Rack

[rorywalsh]

This also has to do with default values not being assigned. If you add a colour() identifier it will show. For example:

groupbox bounds(10, 10, 90, 70), colour(130, 130, 130), text("Filter") fontColour(255,255,255,255)

So it looks like some default values are not being assigned for all widgets. I'll take a look.