Add option to toggle between single last “it” or view all “it”s

```
Currently we only show the last "it" value in the tree view, but might be nice 
to be able to choose between that mode and a mode that shows all "it" values 
ever bound, i.e. "it1", "it2", "it3", ...
```

Original issue reported on code.google.com by `stephen....@gmail.com` on 28 Nov 2011 at 4:07
