Introduce HeaderFooterLayout

A simple C++ based layout which replicates a little part of what Page does, a container with 3 properties, header, contentItem and footer which will be laid out oone on top of each other. It works better than a ColumnLayout when the elements are to be defined by properties by the user, which would require ugly reparenting dances and container items to maintain the layout well behaving. examples where this could be used are Card and GlobalDrawer