mime detection may not cache properly for specific request paths

DefaultMimeSupport has it's own code to extract the extension from a given path. The code doesn't handle certain cases where dots appear multiple times in the path, or when slashes appear after the last dot, which means it can end up extract more of the path than necessary. This can lead to situations where the mime cache is ignored.

DefaultMimeSupport should instead use FilenameUtils.getExtension