Description of changes:

• create a new DLC struct every time a new DLC actor is set up (Core objects should have the life expectancy of the corresponding Python objects #4220)
• use standard exception mechanism in the DLC /DAWAANR/MDDS core setters (Robust exception mechanism in core setters #4219) and test it
• non-P3M methods no longer crash the system with std::abort() (via errexit()) when something unexpected happens
• reduce code duplication in DLC by disentangling DLC from P3M
  • DLC now depends on feature DIPOLES instead of DP3M (aka DIPOLES + FFTW)
  • ICC now depends on feature ELECTROSTATICS instead of P3M (aka ELECTROSTATICS + FFTW)