Update tomee-site-generator to allow examples internationalization

We want to enable Spanish and other languages for the docs and examples section,  Perhaps:

 - http://tomee.apache.org/tomee-8.0/es/docs/
 - http://tomee.apache.org/tomee-8.0/es/ejemplos/

The converstion should look like this for spanish :  

 - https://github.com/apache/tomee/blob/master/examples/cdi-request-scope/README_es.md
 - http://tomee.apache.org/tomee-8.0/es/ejemplos/cdi-request-scope.html

For English (default) the conversion should be the current approach:

 - https://github.com/apache/tomee/blob/master/examples/cdi-request-scope/README.md
 - http://tomee.apache.org/tomee-8.0/examples/cdi-request-scope.html