Put sampled names into IsaCoSy signature

[Chris Warburton]

Fill in the gaps in isacosy-template.

We need function names, function types, function definitions (these must
be given explicitly, but we should be able to just do 'A.foo').

We need variables for each input type. Try all of them to see what
happens; maybe we'll have to be more selective e.g. if there are no
generic data generators, but we can cross that bridge when we come to
it.

Try ignoring the undefined terms (like 'head([])') for now; we might get
away without having to put them in. Otherwise, we can just follow the
error messages.