Add mysql extension for sql scripts (#3413)

samples/Text/filenames/README.mysql

@@ -0,0 +1,24 @@
+README for users interested in using MySQL as a triplestore backend
+===================================================================
+
+The KiWi Triple Store used by Apache Marmotta supports different database
+backends, including H2, PostgreSQL and MySQL. However, for legal reasons,
+we are not allowed to distribute the MySQL connector library together with
+the Apache Marmotta source code or binaries, as it is licensed under GPL
+license.
+
+Nonetheless, it is possible to use MySQL by downloading and installing the
+connector manually:
+    1.  download and unpack the MySQL Connector/J from
+        http://dev.mysql.com/downloads/connector/j/
+    2.  copy the mysql-connector-java-5.x.x.jar file to
+        a. the library directory of the application server
+           (e.g. $TOMCAT_HOME/lib)
+        -- OR --
+        b. the library directory of the Apache Marmotta Web application
+           (e.g. $TOMCAT_HOME/webapps/marmotta/WEB-INF/lib)
+    3.  restart the application server
+
+Apache Marmotta will then automatically be able to use the MySQL connector
+to connect to a MySQL database. Please note that Marmotta requires at least
+MySQL 5.x, because it makes use of nested queries and foreign keys.