bpampel/bdld: v0.3.2

Release that has mostly cosmetic changes, i.e. better documentation and cleaner code

• add recalculate-probabilities option to birth-death action for permanent usage
• rename correction-variant to approximation-variant in code and allow this in the input
• deprecate the correction-variant option (but currently still supported)
• fixed periodic boundary conditions
• fix crash in DeltaF and ParticleDistribution if no filename was specified
• FES is no longer data member of Histogram class but stored as separate grid in the FesAction
• helper functions required only by single action moved to the respective modules
• a lot of added / changed code documentation
• improved / extended tests (BirthDeathAction)
• cosmetic improvements of code