This setting is set to _off_ on some imported animation files;
in this case, tangent data is not used and the curve is interpolated linearly.
Previously, we would sometimes set this to on as part of various animation
manipulations we perform in MA processing; this broke some avatars, e.g. "Fluria".
This adds support for animation mapping for MergeArmature components, as well as supporting locking the position of
MergeArmature-controlled transforms to their original counterparts, to ease animation editing.
With this change it might be best to eliminate the bone proxy component, as it's a bit redundant now.
