ParamValidator: added "oneOf" support for string values and removed a forgotten var_dump() in one of the checks.
SqlConnection now defaults to charset UTF8.
Bug fix: HttpUpload::hasError() used to return the opposite of the intended result.
ImageUtils new features and bugfixes:

- Optional caching of the parsed source image between resize() calls.
- Target image width/height can be given as null to use the source width/height.
- Ability to override the auto-detected source MIME type by supplying an alternate filename or a MIME type.
- If the target filename ends with ".png" we now properly produce a PNG image.
- Comment typos fixed & some refactored code.