ROOT geometry of the CBM magnet

Based on the CAD design of BINP Novosibirsk, November 2018.
MC model by Egor Ovcharenko (evovch@gmail.com).

Version with field clamps, meant for being used with the RICH system (electron setups).

A GDML geometry was created from the original CATIA design files. The GDML geometry was converted into ROOT TGeo format by A. Senger, using the macro macro/geometry/gdml2root.C.

The most substantial difference to the previous geometry (v15a) is the increase in the vertical aperture to 1,440 mm. The field clamps are 190 mm thick.