The mapping library needs to use more of the information provided by the plugins.

Quite a bit of the current code has evolved pretty rapidly from the prototype for the new library, and some things seem to have been left behind a little.

Currently the maximum zoom level and tile size are hard-coded, where they should be set from the values provided by the plugin.

The file extension in QGeoTiledMapReply is also ignored at the moment, and everything defaults to PNG.

We also need to consider whether we want to allow the plugin to provide its own QGeoProjection subclass, or whether we instead just want to stick with Mercator projections and use the QGeoProjection subclasses to switch between projecting to a plane and projecting to a sphere.

These issues need to be addressed.