Remove all prefixes such as I_ from variable names

Please remove all prefixes such as I_ and D_AI_ from variable names in PFS code (e.g. FiberTrace.cc). For parts of stella which haven't evolved in the past few years you may keep them as a grandfathered feature.

I understand that this was a style you used in previous projects, but Hungarian notation is generally deprecated, even for windows, and it is not acceptable in new code.