Add the possibility of having a region defined in an element "element"

[Former user]

It would allow the possibility of having specific production cuts in imported GDML geometries.

Here is an example:

detectorRegion: cutsregion, prodCutPhotons=1e-5;

CENTRAL_SOL: element, fieldAll="detectorfield", geometryFile="gdml:CC_geometry.gdml", l=4.2004, outerDiameter=1, stripOuterVolume=1, region=detectorRegion;