Loads the search config from a XML file. The location of the XML file is
specified by the init parameter "searchConfigFile".
author: Tilman Schneider, STZ-IDA an der FH Karlsruhe
Creates the configuration of the search mask.
Parameters: request - The page request. Used to get the "configFile" initparameter, which holds the name of the configuration file. The configuration of the search mask. throws: RegainException - If loading failed.