New Features

• GdiImageLayerProxy class
• AsyncLayerProxyLayer class
• MiniMapControl (thanks @becio)
• Allow use of SharpSbn spatial index
• Add IMapTool interface to write custom tools for SharpMap.UI
• Add WPF Control wrapping MapBox (thanks @petlof)
• Allow setting zoom by scale (thanks @petlof)
• GeoPackage provider
• SharpDX layer
• Added ISession...