Merge pull request #69 from jlewin/development

Update Print Queue Edit functionality
Fixed a bug with trying to render null meshes.
Starting work on fixing grid on gcode view not being able to be hidden.
Merge branch 'development' of https://github.com/MatterHackers/MatterControl into development
Make 3D view panels visible in edit mode only.
Make 2D view panel visible only after layer data is generated.
Merge branch 'development' of https://github.com/MatterHackers/MatterControl into development
Correct Widget ordering for Remove button