Revert "fix things up"

This reverts commit 2fe40de1b74f9f7b7473b109ce1ed1c1cf341295.
Revert "dynamically creating the variable names is problematic"

This reverts commit 4f71c837a23d3e4e190444f13c65a605f41eb6d9.
Revert "form the strings from symbols properly"

This reverts commit c396b0eed5193f3a6fd8f1f0f69a36dcc2e102d2.
Revert "slopeAspectCurvature takes bools not paths"

This reverts commit 9aa78182f51067d7beec22bc07118ae95cccc642.
Revert "try a little bit of metaprogramming in ta_morphometry"

This reverts commit 97dc3d6db8562707b1edc02282c5cc27ba2090c1.
add ta_channels