Adjust default alignment when switching from inline to block

Once more with feeling; default alignment when switching between
inline to block and vise versa. This time, the problem was mainly
that the checkbox for position cannot be updated without triggering
its update event. It was triggered, however, before setting up the
positioning, which caused the model to run positioning twice and
get things wrong.

Another smaller fix in this commit was done to make sure that
the image model remembers the previous alignment, so when image
type changes from inline to block and vise versa, and the alignment
was default, it can recalculate default value for the new node.

Bug: 65564
Change-Id: I6c16a7855ad7e3ce302fa3d042d0a402251b31f0
Merge "Adjust default alignment when switching from inline to block"