Added ability to specify value associated with the Server header in HTTP responses.

This replaces the server version string from HTTP headers in server responses, by adding the server keyword to the tomcat Connectors in CATALINA_HOME/conf/server.xml.

The default value for this header when it has not been defined in the connector is: Server: Apache-Coyote/1.1.

By overriding default['tomcat']['server_name'] you now have the ability to change the value associated with this header in HTTP responses.

OWASP defines this as a best practice for securing tomcat installations: https://www.owasp.org/index.php/Securing_tomcat 

Please review these changes.