Change writing format

[VEZY]

Our printing of the MTG when we write back to disk takes too many columns e.g.:

^+A1									
^/GU1									
	/N1								
		<N2							
			+A2						
			^/GU1						
				/N1					
				^<N2					
					<N3				
						<N4			
							<N5		
								<N6	
									<N7
									^+Leaf1
								^+Leaf1	
							^+Leaf1		
						^+Leaf1			
					^+Leaf1				
				^+Leaf1					
			<N3						
				<N4					
					0				
					^/GU1				
						/N1			
						^<N2			
							<N3		
								<N4	
									<N5
									^+Leaf1
								^+Leaf1	
							^+Leaf1		
						^+Leaf1			
					<N5				
						<N6			
							<N7		
								<N8	
								^+Leaf1	
							^+Leaf1		
						^+Leaf1			
					^+Leaf1				
				^+Leaf1					
			^+Leaf1						
		^+Leaf1							
	^+Leaf1								

This one can be reduced to the following just by changing the rules that decide when we create new columns, and how we order the nodes:

^+A1		
^/GU1		
^/N1		
	+Leaf1	
^<N2		
	+Leaf1	
	+A2	
	^/GU1	
	^/N1	
	^<N2	
		+Leaf1
	^<N3	
		+Leaf1
	^<N4	
		+Leaf1
	^<N5	
		+Leaf1
	^<N6	
		+Leaf1
	^<N7	
		+Leaf1
^<N3		
	+Leaf1	
^<N4		
	+Leaf1	
	+A2	
	^/GU1	
	^/N1	
	^<N2	
		+Leaf1
	^<N3	
		+Leaf1
	^<N4	
		+Leaf1
	^<N5	
		+Leaf1
^<N5		
	+Leaf1	
^<N6		
	+Leaf1	
^<N7		
	+Leaf1	
^<N8		
	+Leaf1	

Check the rules, but I think that (rapid analysis):

• we shouldn't create a new column if the node has only one child;
• the nodes that follow should stay in the same column, and the nodes that branches should go in a new column, unless they have no siblings
• we should visit the branching nodes first, put them in a new column (unless they have no sibling has I just said), then the nodes that follow (and keep them in the same column as we can't have two nodes that follow I think);
• nodes that decompose should stay on the same column that their parents, unless they have siblings, in that case they should be in a new column (but first, before branching nodes)