do not specify the choice of geometry in the emulator

*** This change will break other people's code and thus the pull request is meant mostly for discussion. ***

I was attempting to match the UCT variables with more complicated offline objects, and this makes the use of more realistic geometries (for real data) important. 

In my end user config, I need to include the following:
process.load('Configuration.StandardSequences.GeometryRecoDB_cff')
which conflicts with 
from Configuration.Geometry.GeometryIdeal_cff import *

Therefore I propose that the emulation code should not be the place to enforce the choice of geometry; it should be chosen in the end-user config (places like makeEfficiencyTree_cfg.py).