Introduce river mapfile generation (WARNING: Changes in config xml files required!). On startup the RiverMapfileGeneratorStarter is called by the server app. The starter invokes a call to RiverMapfileGenerator.generate() which reads all available rivers from the database and generates layers for each river (in theory...uncompleted) in a river.map file. The old MapfileGenerator which generates layers that have artifact dependencies is now in ArtifactMapfileGenerator.

<?xml version="1.0" encoding="UTF-8" ?>
<rest-server>
    <!--  The port which the ArtifactDatabase (ArtifactServer) will bind to. -->
    <port>8999</port>
    <listen>localhost</listen>
</rest-server>