Added command to start datasource

Handy little script to start the datasource with the xcore script itself.  You can currently run it with just `xcore server`.  The logs from the command are written to the console just as if you had run it directly.
I could do something like that, yes, but then the build script would be strongly coupled to the implementation of the server.  This allows the server's implementation to vary as needed without having to modify the build script code at all.