- Color scheme is separate from the display.
 - This allows a coherent color scheme to be used.
 - Also added a standard display.xml and display_detailed.xml (currently
   just a copy)
 - A new color scheme should start with colors2.xml which is currently a
   copy of colors.xml
 - created grouped subsystem includes.

Also began adding subsystems:
 -  compact/subsystem_views/pid_only.xml
 -  compact/subsystem_views/tracking_only.xml
 -  compact/subsystem_views/vertex_only.xml

 - using "athena"
 - this avoids any clashing with the reference detector libraries.

The ACTS layers cannot have overlapping surfaces.
This will likely go away in future when the concept of "layers" is
removed from ACTS geometry.

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