Northwind sample uses DB script, instead of .mdf | .ldf

Consider changing the [Microsoft.Restier.Samples.Northwind](https://github.com/OData/RESTier/tree/master/src/Microsoft.Restier.Samples.Northwind) sample to use DB script, e.g., [instnwnd.sql](https://msdn.microsoft.com/en-us/library/ff851969%28v=vs.100%29.aspx), instead of .mdf and .ldf files.