Revert the changes introduced in v67 of Plasma20

Specifically, we now store 32-bit float times in hsKeyFrame. While storing
a 16-bit short save some space, it introduces many rounding errors due to
the way 3ds Max stores keyframes. This allows non-identical keyframes to
overwrite one another. We don't want that!
Don't compress my quats!
Bump plVersion to 71.0

Controllers are used so far and wide that this is a major version change.