Include datasource plugin

This adds the plugin-datasource to the SDK.

Warning : an artifact must be added to nexus before pulling.
The artifact is the nuodb jdbc driver.
The following installation instruction is copied from the plugin-datasource README.md:


1. Retrieve the driver jar from a NuoDB installation. it should be in jar/nuodbjdbc.jar.

2. Install it :

```
        mvn install:install-file -Dfile={path/to/your/nuodbjdbc.jar} -DgroupId=com.nuodb.jdbc -DartifactId=nuodb-jdbc -Dversion=2.0.3 -Dpackaging=jar
```