WHY IS THIS CHANGE NEEDED?:
- crosscorr process does not have stationary option and therefore will
  not perform calculations correctly if all signals are in-phase.

HOW DOES THE CHANGE SOLVE THE PROBLEM?:
- Additional 'stationary' parameter that tells the process to compute
  the mean over replicates AND time points.

WHAT SIDE EFFECTS DOES THIS CHANGE HAVE?:
- crosscorr process not used anywhere else in aliby, so should not
  affect aliby.
- crosscorr process used in multiple places in skeletons (particularly
  arin's projects).  this is an *additional* parameter, and the existing
  behaviour of crosscorr process is same as stationary=False, so i don't
  expect breaking changes.

EVIDENCE THAT COMMIT WORKS:
- new test to be run

REFERENCES:
- #72

WHY IS THIS CHANGE NEEDED?:
- using dev_testimage.py in skeletons: when dummy tiler is created and
  tiler.initialise_traps() is invoked, segment_traps() (still) raises 'No valid
  'tiling regions found'

HOW DOES THE CHANGE SOLVE THE PROBLEM?:
- in tiler.initialise_traps(), initial_image was defined based on
  self.ref_channel and self.ref_z; however, if ref_z was not 0, then
  initial_image would be a zero array.
- this was because ImageDummy.pad_array() put the input image at the 0
  position and pads with zeros regardless of the value of ref_z.
- so i wanted the output of ImageDummy.get_data_lazy() to be defined in
  such a way that the (ref_z)th slice in the z-direction is the input
  image.
- therefore, i added a new argument to Image.Dummy.pad_array() so
  that ref_z can be used to achieve the above.

WHAT SIDE EFFECTS DOES THIS CHANGE HAVE?:
- tech debt: no (easy) way to deal with ref_channel because it's a
  string.  workaround is to keep the ref_channel the first channel
  in the dummy tiler, and assume that throughout.

EVIDENCE THAT COMMIT WORKS:
- modified test_image.py works
- skeletons: dummy tiler can be defined and dummy_tiler._run_tp(0) runs
  without errors

WHY IS THIS CHANGE NEEDED?:
- when tiler.initialise_traps() is invoked, "No valid tiling regions
  found" is raised from traps.segment_traps() (aliby.tile.traps).

HOW DOES THE CHANGE SOLVE THE PROBLEM?:
- the image called by segment_traps() was a blank image.
- this was because tiler.initialise_traps() uses the first timepoint to
  define the initial image (line 400 in tiler.py).
- the first timepoint was a blank image because ImageDummy.pad_array()
  added zero arrays BEFORE the input array.
- so fixed it by reversing the behaviour of ImageDummy.pad_array()
- and modified the test_image test to reflect this change.

WHAT SIDE EFFECTS DOES THIS CHANGE HAVE?:
- none known -- only potential effect is the test, which was modified

EVIDENCE THAT COMMIT WORKS:
- test_image passed

WHY IS THIS CHANGE NEEDED?:
- test dummy tiler, see if it crashes

REFERENCES:
- issue #53

WHY IS THIS CHANGE NEEDED?:
- https://git.ecdf.ed.ac.uk/swain-lab/aliby/aliby/-/jobs/56786 because
  AttributeError: 'function' object has no attribute 'shape'

REFERENCES:
- issue #53

WHY IS THIS CHANGE NEEDED?:
- https://git.ecdf.ed.ac.uk/swain-lab/aliby/aliby/-/jobs/56781 failed

REFERENCES:
- issue #53

WHY IS THIS CHANGE NEEDED?:
- https://git.ecdf.ed.ac.uk/swain-lab/aliby/aliby/-/jobs/56767 failed
  because ValueError: The truth value of a Array is ambiguous.

HOW DOES THE CHANGE SOLVE THE PROBLEM?:
- use numpy.array_equal() to compare arrays instead

REFERENCES:
- issue #53

WHY IS THIS CHANGE NEEDED?:
- https://git.ecdf.ed.ac.uk/swain-lab/aliby/aliby/-/jobs/56762 failed
  because TypeError: compute() takes 1 positional argument but 2 were given

HOW DOES THE CHANGE SOLVE THE PROBLEM?:
- corrected a stupid typo: compute() is a function that takes no
  arguments that gives out an array, and i want to index that array

REFERENCES:
- issue #53

WHY IS THIS CHANGE NEEDED?:
- https://git.ecdf.ed.ac.uk/swain-lab/aliby/aliby/-/jobs/56757 failed
  because TypeError raised: 'int' object is not iterable

HOW DOES THE CHANGE SOLVE THE PROBLEM?:
- @pytest.mark.parametrize() takes an iterable, e.g. a list -- I forgot
  about it.  fixed it by putting the values in a list.

REFERENCES:
- issue #53

EVIDENCE THAT COMMIT WORKS:
- issue #53

REFERENCES:

Relates to #52

WHY IS THIS CHANGE NEEDED?:
- need a simple test to see if gitlab visualises coverage

HOW DOES THE CHANGE SOLVE THE PROBLEM?:
- write a test for interpolate post-process; this test checks that
  interpolated values are as expected by leveraging a dummy signal that
  is a gradient.

REFERENCES:
- issue #46
- merge request !8