Illustrates how to import data from a Vector Product Format (VPF) database into World Wind. This uses 
VPFLayer to display an imported VPF database, and uses 
VPFCoveragePanel to enable the
 user to choose which shapes from the VPF database to display.
 
 To display VPF shapes with the appropriate color, style, and icon, applications must include the JAR file
 
vpf-symbols.jar in the Java class-path. If this JAR file is not in the Java class-path, VPFLayer outputs
 the following message in the World Wind log: 
WARNING: GeoSym style support is disabled. In this case,
 VPF shapes are displayed as gray outlines, and icons are displayed as a gray question mark.