Implement Tomita Parsing

[SamyaDaleh]

It is similar to LR-parsing, but works nondeterministic. The items can contain lists of stacks. One stack could be "0-s-1-prep-6". Or trees if two sup-processes do the same (like ...1-prep-6). Or it can be graph-structured as in our lecture, like an extension of the tree. But I don't have a representation for that. Better stick to the first option for now. Goal item is "accept".