Support conversions from db type to string properties

[dazinator]

Suppose your POCO object has a string property, but the value returned by the stored procedure is a different type, like int. At the moment this throws an exception saying int cannot be converted to string property. Would be good to handle the conversion to string automatically if there is isn't a "loss" of information caused by the conversion (other than type information).

[snickler]

I can look into this, or if you want to take it on feel free to make a pull request.