Add muonLayout option to VP1

Hi @rbianchi, @emoyse,

I think, we do not need the vp1NSW option in VP1 since a given ATLAS layout will tell VP1 if a NSW is present or not. However, for me, it would be quite useful to have an option to specify a muon layout to be displayed. I propose the following changes. With them, you could run vp1 -muonLayout=MuonSpectrometer-R.09.00.AsymNSW and the asymmetric NSW layout would be displayed.

However, I have one question: When running like this, I see that all muon DetFlags are true (which makes sense since I have CSCs and MMs/STGCs). However, in the geometry display, I can turn on the old detectors (and I see e.g. the CSCs only on the Cside), but when I click on 'NSW' I don't get anything displayed. What am I missing here?

Also related: How much effort would it be to extend the VP1 GUI such that the NSW checkbox is replaced by 2 checkboxes (MM and STGC) such that one can turn on and off the subdetectors separately?

Thanks, Nico