optional dependency path resolution conflicts when more than 1 path leads to one real dependency

[r0ller]

As the subject indicates, when more than one optional dependency paths are found that lead to the same real dependency node, there's a conflict in the resoltuion. To avoid that, a rule should be introduced, that takes only the first optional dependency path found into account. So e.g. when the sentence "show location of abc" is evaluated where there are two dependencies for "of" like a constant "CON" and "RESTAURANT" where the constant is the first dependency and the restaurant is the second, then the first optional path leading from "show" to "abc" will be taken into account: show(location(of(con(abc)))). So this has an effect on the design of dependencies as well in depolex.