CoordinateMousePositionPanel starts with NaN

[geographika]

The BasiGX.view.panel.CoordinateMousePositionPanel starts with the X and Y text boxes displaying NaN and a red error underline as shown below:

To avoid the red error underlining when opening the app the view model can be set to show zeros instead:

            viewModel: {
                data: {
                    xVal: 0,
                    yVal: 0
                }

Alternatively the map's starting center could be used (pull request to follow).

[dnlkoch]

Closed via #522.