Centralize preprocessing and fix test validators

• Move repeated preprocessors into a new module GaudiExclusions
• Work around gaudi/Gaudi#108 by inserting the normalizeEOL preprocessor
• Exclude counter/histogram headers so that they do not confuse the parsing
• Add a preprocessor to remove garbage characters printed by LHAPDF
• (Technical) updates to references
• Fix validator of gauss-config-low-energy-cuts test
• Remove reference testGauss-redecay.ref (unused since !524 (merged))

This fixes most test failures in the lhcb-sim10 slot. What remains failing is

• gauss-signalflag-fullsim and gauss-signalflag-skipg4 for which an options file is missing $GAUSSROOT/tests/options/testGauss-SignalFlag.py
• gauss-gen-14165011-pythia6 consistently times out (even with a 3600 s timeout instead of 1800 currently)