Some work on parameter classes, a bugfix on the splitting algorithm
some simplifications in the generation stage

laplace is again proceeding to code generation

UFL did not like  my way of replacing some args with 1 as it
destroyed the shape information. It now remains in the expression,
but triggers code generation separately.

and remove old implementation

It was nonsense, as it did everything done lateron anyway.

Introduce a new topsum splitter