Added MongoDatabase option in the config.yml

Use 'DataStore:mongdb'
Requires Mongo Java driver in plugins/driver/mongo.jar
![image](https://f.cloud.github.com/assets/2925395/1848161/7eb47a1a-767d-11e3-8524-c0a50951eeca.png)
![image](https://f.cloud.github.com/assets/2925395/1848174/c885a2ae-767d-11e3-9fa4-3c89d524cb59.png)