[Rivet] Cuts rewrite: projection sorting

[David Grellscheid]

Hi again,

The code I checked in is probably not functional for the following
reason: I have no idea how to identify when two purely cuts-based
projections are the same.

At the moment cuts are not included in the CMP function for projections
so some projections may get skipped because all of them look the same
right now.



The way we're constructing the Cut objects, it is not easy to determine
that the following cuts a and b are the same:

> Cuts a = Range(Cuts::eta, -5, 5) & (Cuts::pt >= 10);
> Cuts b = (Cuts::pt >= 10) & Range(Cuts::eta, -5, 5);

  David