Token tree organization rules
-----------------------------

Each node must have rules for the sub-nodes allowed. These rules follow the
regexp syntax.

.------.
| Node | +-> Node
`------' |
         +-> Node
				 |
				 +-> ...
				 
1) Specific rules.
   
	 - Any number of these rules allowed.

   - Each rule specifies a regexp pattern, and a number specifying how many
     nodes matching this rule are allowed. 0, a specific number, or any amount.

   - If a node matches more than one rule, the lowest number is used. This
	   means that if a node matches both a 0 rule and a 1 rule, the 0 rule is
     applied, meaning the node is rejected.
		 
2) General rules.

   - One such rule allowed.

   - Inherit rules from predecessor.
