Resuscitate the CTP7 ME0 flavor

[Based on top of !174 (merged).]

As the usage of a µTCA-based system is envisioned for the first ME0 test beam(s), this MR resuscitates the CTP7 ME0 flavor, bumping the number of supported layers to 6. The first commit introduces only 4 layers with trivial fiber mapping on the 3 CXP while the last commit introduces 2 additional layers with less trivial fiber mapping on the MTP48 connector while disabling the ME0 S-bit clustering.

No major changes are included. It is however recommended to review commit by commit in order to (1) have access to their comments and (2) avoid getting tricked by large diffs only due to formatting.