New strip cpe

Updates the strip rechit resolution parameterization.

Presented in the offline reco meeting here:
https://indico.cern.ch/event/330430/session/5/contribution/18/material/slides/0.pdf

The summary of the work, including pointers to previous presentations and code locations can be found at this tracker DPG meeting:
https://indico.cern.ch/event/305424/session/0/contribution/25/material/slides/0.pdf

In addition to a presentation on the impact on alignment:
https://indico.cern.ch/event/305425/session/0/contribution/17/material/slides/0.pdf
indeed
also in
https://twiki.cern.ch/twiki/bin/viewauth/CMS/SiStripCPE there seems to be a clear difference between "expected cluster width" (uProj) and "cluster width" (N?)