Don't build an imageset for a filter if there is no imageset and we ask for images.
Added enumerator for imageset images
Added ability to change image extension
Extended cleanup pipeline to ensure images in an imageset have the correct filename.  Used for RC2 where the names change when sections are reordered.
Added missing property tag
Check the full image path during existence test
Added a function to update the image files referenced in .stos files which are incorrect if sections are re-ordered. Added this to the Cleanup pipeline.
Centralized the generation of default image names for filters.
Nice error when cannot find ControlFilter or MappedFilter for StosGroup
Additional tests
Workaround for crash in logerr.  OK to add back in later versions after debugging.
Version bump
Add default value to ImageExtension
Update to Numpy 1.9.1 which has some nice performance improvements
Test fix and debug output clarity
Fixed missing level tag in downsampled imageset
Changed import, forgot to revert.  It passes tests so the change stays.
Merge branch 'dev'
Merge branch 'master' into nornir-master