Cleanup myconfig features

[jngrad]

Description of changes:

• remove unused features
• improve documentation of interaction features

[codecov]

Codecov Report

Merging #3740 into python will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           python   #3740   +/-   ##
======================================
  Coverage      89%     89%           
======================================
  Files         552     552           
  Lines       24513   24513           
======================================
  Hits        21836   21836           
  Misses       2677    2677           

Impacted Files	Coverage Δ
src/core/energy_inline.hpp	84% <ø> (ø)
src/core/forces_inline.hpp	91% <ø> (ø)
src/core/particle_data.cpp	96% <0%> (-1%)	⬇️
src/core/electrostatics_magnetostatics/p3m.cpp	87% <0%> (+<1%)	⬆️

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