Make it possible to resize rectangles to their minimum size

After creating a node of minimum size (as defined in
DefaultLayoutConstants) it was possible to make the node larger, but not
to resize it to its original size.

In EObjectRectangularResizableContentControllerBase, the minimum size
did not consider insets.

Issue-Ref: 3924
Issue-Url: https://af3-developer.fortiss.org/issues/3924


Signed-off-by: Ulrich Schöpp <schoepp@fortiss.org>