[Rivet] Z projection on Rivet

[David Grellscheid]

Hi,

> Ok, I'm starting to wonder whether we should put all of this into the 
> ZFinder projection or give up having a uniform ZFinder and do all of 
> this stuff "manually" in the analyses. Opinions?

I find the ZFinder useful, so would argue for making it more powerful. 
Also, debugging-wise it's extremely helpful to concentrate all future 
implementation mistakes in one place. :-)

   David