Listen to markers

[uliska]

I've now (finally) taken a look at the listen-rehearsal-mark branch, at least on the example file, and I have a few questions:

In general I think it is a very good thing to have mods relative to such hooks, as this will make them more robust for a significant number of use cases where the time structure of a score isn't completely pre-set.
However, it's not always acceptable to be forced to add a rehearsal mark for that. So: is it possible to use invisible marks as hooks, either by making an explicit \mark invisible or (rather?) by introducing a new type of object? So the user would insert some thing like a \eeHook "sectionA" somewhere and the mod refers to that.

I think the naming \editionModMarked should be reconsidered. When reading the example file I wouldn't have guessed what that means. That name rather indicates that something has been marked - rather what we are looking forward with the IDs.
Maybe it would be better to integrate the functionality in the \editionMod command as an option?

[jpvoigt]

1. The name is just s scrap-name. Perhaps we find a reasonable name, when we solved 2.
2. I used rehearsalMarks as a first solution. An eeHook- or eeMark-event would be a good thing. They could optionally produce a RehearsalMark. So the rehearsalMarks are used here, to have a working solution right now, but that shall not be the final state.