Blender Git Loki

Follow-up commit to r.41765

Reviewed behaviour of selection operators, and decided that ultimately, it's
better if select left/right/column didn't change the channel selections at all.
This is because with the highlighting of the active curve nowadays, it's a bit
distracting to suddenly lose track of it after performing these operations, when
you may have been trying to select all of the keyframes on that curve for
further tweaking.