World without layers

Layer objects got more and more the functionality of Volumes.

Actually it only needs:

DetectorVolumes with boundary portals

InternalDescriptors:

ContainerDescriptor for navigation in the volume hierarchy
LayerDescriptor for volumes representing a layer
BoundingHieararchyDescriptor for volume representing a BB hiearachy

This will be tested on a new DetectorVolume which will replace eventually the TrackingVolume, this should help for ITk, ATLAS TRT, ATLAS Calorimeter, etc.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information