TreeReference toString renders 1-based multiplicities by default

[dcbriccetti]

Problem description

TreeReference toString renders 1-based multiplicities by default. This is confusing, especially
in the debugger when looking at something like the following:

Is it safe to change the default?

If not, we could do something like this to change the default when testing:

Thoughts?

[lognaturel]

I don't understand the implications of changing the default. I know at some point there was Collect code that used the toString and expected 1-based indexing but I'm not sure whether that's the case anymore.

I like the Scenario-only fix for now, thanks for suggesting it.