Don't add redundant frame axis to corrected output of single-frame data for slow detectors

Pointed out by James, the data output for Epix100Correction needlessly has a frame axis in front - like the faster detectors. Am just using OVERWRITE_ELEMENT to change dataFormat.outputAxisOrder default and options; could also deepen class hierarchy to single-frame and multi-frame detectors, but that seems like a lot of work if this is the only override really needed.