* modify NXtomo behavior when no image_key_control: previously it was trying to get some 'return' projections from rotation angle. This was a non sense. It has been removed.
* check detector dataset - log warning if virtual dataset is broken or appear to contain more external file than the OS can handle
* check detector dataset - log warning if virtual dataset is broken or appear to contain more external file than the OS can handle (PR 147)
* misc
* increase usage of f-strings when possible (PR 71)