TEST: Move tests into fsl package

fsl/tests/test_filetree/format.tree

fsl/tests/test_filetree/local_parent.tree

fsl/tests/test_filetree/parent.tree

fsl/tests/test_filetree/parent/opt_file_test.nii.gz

.../test_filetree/parent/opt_layer_test/opt_file_test.nii.gz

...test_filetree/parent/opt_layer_test/opt_file_test2.nii.gz

...tests/test_filetree/parent/opt_layer_test/sub_file.nii.gz

fsl/tests/test_filetree/parent/sub_file.nii.gz

fsl/tests/test_filetree/test_query.py

fsl/tests/test_filetree/test_read.py

fsl/tests/test_filetree/test_registration.py

fsl/tests/test_filetree/test_template.py

fsl/tests/test_fixlabels.py

fsl/tests/test_freesurfer.py

fsl/tests/test_fsl_data_utils.py

fsl/tests/test_fsl_utils_path.py

fsl/tests/test_fslsub.py

fsl/tests/test_gifti.py

fsl/tests/test_idle.py

fsl/tests/test_image.py