Paying attention to following items:
* Overall parameterization -- will use for optimization
* Constant naming consistency
* Documentation via the comments
* Added new ci job which concatenates all the `<comment>` tags into `docs/detector.md`
* All comments should now be formatted to fit the appropriate section in the markdown file.

- Renamed the vertex and tracker barrel detectors
- Commented out endcap tracker
- Added more detailed to space frame construction.

 - Broke TRD into to planes (per the ref. detector image).

	modified:   compact/display.xml

	modified:   compact/vertex_tracker.xml

Fixed ce_GEM overlap

 - CylinderTrackerBarrel_geo can be used to define detailed modules
 which are then placed in barrel array.
 - The modules are cylindrical segments of a tube.
	modified:   compact/definitions.xml
	modified:   compact/gem_tracker_endcap.xml
	new file:   compact/mm_tracker_barrel.xml
	modified:   reference_detector.xml
	new file:   src/CylinderTrackerBarrel_geo.cpp

 - Uses the TrapEndcapTracker geometry construction
 - Material thicknesses needs attention.

	modified:   ../reference_detector.xml

 - Vertex tracker endcaps are simple disk trackers.

Dmitry Romanov authored 3 years ago and Whitney Armstrong committed 3 years ago

	modified:   reference_detector.xml

	modified:   compact/definitions.xml
	new file:   compact/forward_romanpot.xml
	modified:   reference_detector.xml

	new file:   compact/B0_tracker.xml
	modified:   compact/definitions.xml
	modified:   reference_detector.xml
	new file:   src/ref_RectangularTracker_geo.cpp

 - Currently just a volume  containing air.

 - Added some fudging numbers for ecal endcap z positions. Should fix
 this in the future..