MongoDB Datasource [Bug fix]: Output XML generated by GA

I changed ConfigWriter because, when using MongoDBDataSource with the GA, it threw a NullPointerException, caused (I guess) because the variable "name" in  

> pp.endElement(name); 

was null.

Don't know if this solution matches your original design. If it doesn't, maybe you should specify it in the documentation (https://github.com/larsga/Duke/wiki/Datasources#custom-data-sources) either if it's necessary to change the ConfigWriter class or what's the specific structure a customer datasource should have.

Thanks :)