Removed the DataSourceConnectionSource and the <DriverManager> plugin for the JDBC Appender. It is not safe to use. Please use the DataSource or factory connection sources backed by a connection pool.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1565838 13f79535-47bb-0310-9956-ffa450edef68