reverted setting (and maybe inheriting) draw order for global animations

Although this feature seems to be quite useful (setting draw order for
main animations once, and let animation parts inherit the draw order
from the main animation if it is not defined for the animation part),
it would have to be implemented for all other attributes, too (like X
and Y position of the main animation and animation parts, for example),
so it seems to be better to not make an exception for this specific
attribute.

This reverts commit 895d5cb3.