cleaning, refactoring, spelling, spacing
This MR is a somewhat random collection of minor fixes that were accumulated over the past months.
It removes several unused methods, has some minor refactoring, and improves spelling and spacing.
In particular src/Classic/AbsBeamline/Bend2D.cpp
and src/Elements/OpalBeamline.cpp
were cleaned.
Some of the fixes were found with the static code analysis of #62.