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.

This MR has no effect on any production workflow.