Renamed the "adder" variables to "add" for more DSL-ness.
Changed MD2's result's repr to be more descriptive.
Changed Constraint to a toplevel trait.
Made constraints able to vary the note based on the severity of the violation.
Made adders able to deal with DissectorOs.
Added a helper trait for typical constraints with two notes.
Added operators for conveniently attaching constraints to dissectors.
Added some contraints that are likely to be commonly encountered.
Sprinkled constraints on the MD2 dissector.
Changed the toplevel comment in MD2.scala into a more formal form.

Something like this will become the standard form for toplevel comments
in dissectors.