Better functionality for producing combinations of file inputs and parameters

[samuell]

Right now there is the FileCombinator and ParamCombinator for producing combinations / "permutations" based on streams of either files or parameters.

We either also need a combined component for boths files and parameters, or some more general functionality for this, e.g. built into the port methods.

For example, something like:

// <snip>
proc2 := wf.NewProc("proc1", "some command {i:infile} {p:param1}")
proc2.In("infile").From(prpc1.Out("out"))
proc2.InParam("param1").FromStr("1", "2", combine="crossprod")
// ... in order to run each incoming file from proc1 with param1 set both to 1 and 2.