Move derby logs generated during unit tests to target/

.gitignore

 sonar-server/src/main/webapp/deploy/plugins
 sonar-server/src/main/webapp/deploy/jdbc-driver.jar
 sonar-server/src/main/webapp/deploy/maven/org
-plugins/sonar-core-plugin/derby.log
+sonar-server/src/main/webapp/WEB-INF/log/
 
 # javadoc
 docs.tar

sonar-testing-harness/src/main/java/org/sonar/test/persistence/DatabaseTestCase.java

 
   @BeforeClass
   public static void startDatabase() throws Exception {
+    System.setProperty("derby.stream.error.file", "target/derby.log");
+
+    /*
+    Note: we could use a datasource instead of a direct JDBC connection.
+    See org.apache.derby.jdbc.ClientDataSource (http://db.apache.org/derby/papers/DerbyClientSpec.html#Connection+URL+Format)
+    and org.dbunit.DataSourceDatabaseTester
+     */
     EmbeddedDriver driver = new EmbeddedDriver();
     DriverManager.registerDriver(driver);
     databaseTester = new JdbcDatabaseTester(driver.getClass().getName(), JDBC_URL + ";create=true");