Creates a new MDI (Multiple Document Interface) object. Class specific
%OPTIONS are:
-minsize => [X, Y]
specifies the minimum size (width and height) in pixels;
X and Y must be passed in an array reference
-maxsize => [X, Y]
specifies the maximum size (width and height) in pixels;
X and Y must be passed in an array reference
-minwidth => N
-minheight => N
-maxwidht => N
-maxheight => N
specify the minimum and maximum size width
and height, in pixels
-topmost => 0/1 (default 0)
the window "stays on top" even when deactivated