split map layer selection dialog
integrate Wikiwides multi-layer patch (thanks ! :-) ); use a list model to represent the map layers
refactor main map object access
optional debugging statement
make possible for children to determine available height
in case a sub-flickable is used (like a list view), move the header to cover the flickable overflow
The background rectangle is used as background in list views and grids

It also has the active property that can be used when the component is used as a simple button.
initial version
overlay support
move the initial layers assignment
make the slider set layer opacity
add OSM transit overlay
add/remove overlays
make the remove button visible only if there are some overlays
fix list view viewport; make the mouse area fill the the last item buttons
use layer names, sue shorter prefix in layer list
improve documentation
return layer object instead of just returning a layer id string
print layer name when setting a layer
enable setting layers