[Rivet] New projection method names without "projection"

[Frank Siegert]

Hi Andy,

> As some of you at the MCnet Computing School last week (which was excellent,
> by the way) know, I think we made a mistake when we used the word
> "projection" to name a concept in Rivet.

For those of us who were not at the school last week, could you
explain why Projection is a misnomer? I always liked it, as it is a
concise wording which still captures exactly the functionality.

> We're too far down the rabbit-hole to completely reverse that now, but we
> can reduce the number of times that normal users have to encounter the word
> "projection".

I'll admit to being a boring conservative here, who has been scolded
too often for user-facing changes (though I think we have been pretty
good over the last months or even year(s)). While I'm not strictly
against such changes, I'd prefer to limit them to really good reasons.

> For addProjection, the "Projection" part of the name is redundant because
> the argument type is an object derived from Projection. But I don't think
> "add" is a very clear name anyway, so maybe something like register(myproj,
> "MyObs") would be better? We could have "add" as another alias to ease the
> transition from addProjection.

Would the plan be to leave all three  (addProjection, register, add)
functioning forever, or would one or two be obsoleted at some point?

Cheers,
Frank