revert usage of numeric conversion in parameter retrieval since these can be strings; fixes restart regression tests

 zero but bunch is at e.g. z = 10 m; reintroducing __DBGMSG__ define
which is useful for debugging printing the name of the file without its
path and the line number

Issue 273

See merge request !51

Closes #273

deleted:    src/Distribution/MagneticField.cpp
deleted:    src/Distribution/MagneticField.h

modified:   ../Classic/AbsBeamline/Cyclotron.cpp
modified:   ../Classic/AbsBeamline/Cyclotron.h

modified:   ClosedOrbitFinder.h
modified:   Distribution.cpp
modified:   SigmaGenerator.h

Merge branch '254-reduce-code-duplication-in-ccollimator-probe-septum-and-stripper-with-common-base-class' into 'master'

Resolve "Reduce code duplication in CCollimator, Probe, Septum and Stripper with common base class"

Closes #254

See merge request !50