Merge branch 'enh/transforms' into 'master'

CHANGELOG.rst

README.rst

doc/_static/theme_overrides.css

doc/conf.py

doc/contributing.rst

doc/fsl.rst

doc/fsl.scripts.fsl_convert_x5.rst

doc/fsl.scripts.rst

doc/fsl.transform.affine.rst

doc/fsl.transform.flirt.rst

doc/fsl.transform.fnirt.rst

doc/fsl.transform.nonlinear.rst

doc/fsl.transform.rst

doc/fsl.transform.x5.rst

doc/fsl.utils.rst

doc/images/fnirt_coefficient_field.png

doc/images/fnirt_coefficient_field.xcf

doc/images/fnirt_warp_field.png

doc/images/fnirt_warp_field.xcf

doc/images/nonlinear_registration_process.png