WithIntParameter to convert params from int to string 

We convert params from int to string all over the place
And from decimal in a few places
and we don't always do it the same way
So centralise it and it the long-winded right way just once (in `ParameterExtensions.cs`) and use that internally and expose for external use. 
New extension methods are `WithIntParameter(name, value)` and `WithDecimalParameter(name, value)`