Remove SqlClient namespace dependency

[FransBouma]

In the LLBLGen Pro query engines we don't use any ADO.NET specific namespaces and the db engines in Linq to Sql2 should not depend on any external namespace. This requires additional code, especially ADO.NET specific type setters on DbCommand instances, in the form of IL generated delegates. This code is available in the llblgen pro runtime and we can just copy over these classes to make the Linq to Sql 2 code independent of any ado.net provider namespace.

This is required to be done before any other major work as code can be made much more db independent because of this.