HTML Widgets; Grid; Allow column colouring to visually keep similar columns together

The ability to specify a background colour for a widget.UI.Grid column has been added.

This should be used sparingly but can be used to visually keep related columns grouped together, e.g.:

C.gridItems.AddColumnCode("MonitorCategoryAId", { caption: "Test", backgroundColour: "rgba(255,0,0,0.1)" });