Fix #4357.`identify` returns a type, not a class name, and this result is not always usable for createReader. The docs say that it is usable in that manner. Changing the behavior of `identify` would be a breaking change, but adding an optional parameter (defaulting to current behavior) allowing it to return a class name rather than a type would not. This PR adds that parameter and updates the documentation to suggest its use for the code in question.
To complete this change, `createReader` now accepts either a type (current behavior) or class name (new). Although it is not particularly identified as a possible problem by the issue, `createWriter` is similarly changed for consistency's sake.
oleibman