Commit
              11662b9ad995de173f11dd3bae99e711723e025a
              by peter.peqGenerics refactor
- move variable binding to its own type "VariableBinding"
- VariableBinding now knows what the free variables are
- the match method now knows on which side variables occur (Wurst will 
always only have at most one side with type variables)
fixes #775
 (commit: 11662b9)