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.

SYMBOLSET
SYMBOL
  NAME 'point'
  TYPE ELLIPSE
  POINTS
    1 1
  END
  FILLED TRUE
END
SYMBOL
  NAME "square"
  TYPE VECTOR
  POINTS
    0 0
    0 1
    1 1
    1 0
    0 0
  END
  FILLED TRUE
END
END