Added OpExport2DImage
Rewrote OpStackWriter:
- Iteration axis is simply determined by the order of the Input axistags
- Filepath and filename are provided together in one slot (FilepathPattern)
- FilepathPattern slot expects a format string allowing the user to specify how to name the files.
- Image format is determined by extension in FilepathPattern
- Uses lazyflow.utility.BigRequestStreamer instead of implementing its own request streaming.
- Export is triggered by a function call, run_export(), instead of via a special outputslot.
RoiRequestBatch: Assert of the slot returns 'fake' request objects.
wip