The TRT Lite Detector Factory can update the gas mixtures.

The TRT Lite Detector Factory can update the gas mixtures.

The TRT software community has signaled the need for the TRT gas to follow
changing conditions data during different simulation runs.  This MR  accesses
the conditions data in the "Lite" version of the detector factory. It then
navigates to volumes held within the serial transformers and updates their
gas mixture, taking advantage of the mutability of materials, introduced
specifically for this purpose.  This happens in both the barrel and the
endcaps For the moment the gases are build in the code; when GeoModel I/O
allows us to publish prebuild materials we can instead take those materials
from the database.