omit main class to allow setting it via -Dexec.mainClass

pom.xml

@@ -57,7 +57,6 @@
                     </execution>
                 </executions>
                 <configuration>
-                    <mainClass>info.kwarc.mmt.errorview.SearchDB</mainClass>
                     <cleanupDaemonThreads>false</cleanupDaemonThreads>
                     <killAfter>-1</killAfter>
                 </configuration>