…cit_length_sequences

DICOM: fix multiframe encoding with explicit length sequences

Docs: Explicitly specify English language to Sphinx

ReadTheDocs: updates to fix render

This also falls back to using the (deprecated) imp module to support
Python < 3.5

add support for python importlib to locate MRtrix3 python libraries

See discussion on #2747

This is to avoid failures on macos (where this test was previously being
performed) due to the python distutils package now being deprecated and
no longer available on homebrew.

configure: revert to -isystem rather than -idirafter

Update header copyright to 2024

Allow filename in write_mrtrix.m to be string or char array

Docs: New page on MRView "lock to image axes"

Multiple occurrences of "-Wunused-but-set-variable" that appeared on Mac OSX GitHub CI.

- For mrcolour, output images are clamped to [0.0,1.0] range, so use absolute tolerance rather than fractional.
- Increase tolerance on tckresample -step_size given the imprecision of the resampling operation itself.

CI: Fixes for MacOSX ARM64 runner

Conflicts:
	.github/workflows/checks.yml
	bin/dwicat
	build
	cmd/dwi2mask.cpp
	cmd/fod2fixel.cpp
	configure
	core/app.cpp
	core/file/dicom/element.cpp
	core/file/tiff.cpp
	core/file/tiff.h
	core/filter/dwi_brain_mask.h
	core/filter/fft.h
	core/fixel/types.h
	core/formats/tiff.cpp
	core/image_io/fetch_store.cpp
	core/image_io/fetch_store.h
	core/image_io/tiff.cpp
	docs/reference/commands/dwibiascorrect.rst
	docs/reference/commands/dwinormalise.rst
	package_mrtrix
	python/bin/mrtrix3.py
	run_tests
	src/dwi/directions/set.cpp
	src/gui/mrview/file_open.cpp
	src/gui/mrview/file_open.h
	src/gui/shview/file_open.h
	src/registration/transform/robust.cpp
	src/stats/permstack.cpp
	src/stats/permstack.h
	testing/cmd/testing_diff_fixel_old.cpp
	testing/cmd/testing_diff_matrix.cpp
	testing/cmd/testing_diff_mesh.cpp
	testing/cmd/testing_diff_peaks.cpp
	testing/cmd/testing_diff_tck.cpp
	testing/cmd/testing_diff_tsf.cpp
	testing/cmd/testing_unit_tests_bitset.cpp
	testing/cmd/testing_unit_tests_icls.cpp
	testing/cmd/testing_unit_tests_ordered_queue.cpp
	testing/cmd/testing_unit_tests_parse_ints.cpp
	testing/cmd/testing_unit_tests_shuffle.cpp
	testing/src/diff_images.h
	testing/src/unit_tests/tractography/roi_unit_tests.h
	testing/src/unit_tests/unit_test.h