Added planning for new auto layout-based uiBoxes for OS X.

redo/alboxplan

@@ -0,0 +1,35 @@
+Layout:
+
+	0123456789ABCDEF0123456789ABCDEF
+	[edit0                         ]
+	[button0       ][button1       ]
+	[button2       ][button3       ]
+	[checkbox0            ][b][b][b]	(4, 5, 6)
+	[l]									(label0)
+	(stretchy space       )+-------+
+	(stretchy space       )|       |
+	(space   )[b](space   )| area0 |    (7)
+	(stretchy space       )|       |
+	(stretchy space       )+-------+
+
+The visual layout has to be
+
+	H:|[edit0]|
+	H:|[button0(>=0)][button1(==button0)]|
+	H:|[button2(>=0)][button3(==button2)]|
+	H:|[checkbox0(>=0)][button4][button5][button6]|
+	H:|[label0]				(note the lack of trailing |)
+	H:|->=0-[button7]->=0-[area0]|
+	V:|[edit0][button0][button2][checkbox0][label0]->=0-[button7]->=0-|
+	V:|[edit0][button0][button2][checkbox0][label0][area0(>=0)]| (TODO is this one necessary?)
+
+The problem now is that an empty box has to be represented by something. In the above hand-made example (which I have to test; TODO) we worked around the spaces. How do we do the same in code?
+
+The lower part of the box above is itself a single box laid out like so
+
+	hbox0:	[stretchy vbox0][area0]
+	vbox0:	[stretchy xbox0][hbox2][stretchy xbox1]
+	hbox2:	[stretchy xbox2][button7][stretchy xbox3]
+	xbox*:	[empty box]
+
+Do we need to start representing empty boxes using NSViews?