Support ADO.NET compatible provider names in connection settings

Rhino-Etl expects assembly qualified type names of connection classes in the ConnectionStringSettings.ProviderName property. This deviates from regular ADO.NET usage and causes issues if connection strings in the configuration file are used by non Rhino-Etl code.

Rather than specifying in the app.config file:

    <add name="test"
       connectionString="Data Source=.\SQLExpress;Initial Catalog=test;Integrated Security=SSPI;Timeout=30;"
       providerName="System.Data.SqlClient.SqlConnection, System.Data, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/>

The following should be sufficient:

    <add name="test"
       connectionString="Data Source=.\SQLExpress;Initial Catalog=test;Integrated Security=SSPI;Timeout=30;"
       providerName="System.Data.SqlClient"/>