Fixed initial position and set center not working
Added means to preserve non-map actors
Fixed missing tiles when zoomed in
Silenced debug messages
Center is lat lon
Fixed some more boundary conditions
Add vtkMapMarker, draws image at specified map coordinates

Code currently requires vtkMap to load image file
Fix problems with marker display

* Register ImageData so that it's persistent
* Explicitly load image file for markers (hard-coded file path)
* Add markerteal.png file for initial marker image
* Add vtkMap::AddMarker() method
* Use workaround until we can transform map coords to screen coords (pixels)
Added API to transform latlon to display coordinates
Added API to get center of the map
Fixed transformation methods