Density dependent mortality for consumers

[evadelmas]

New feature: possibility to pass a function to model_parameters to set density dependent mortality for consumers (keyword dc) and producers (keyword dp). Default is no mortality.

[codecov]

Codecov Report

Merging #84 into next will increase coverage by 0.1%.
The diff coverage is 100%.

@@           Coverage Diff            @@
##             next     #84     +/-   ##
========================================
+ Coverage   88.09%   88.2%   +0.1%     
========================================
  Files          15      15             
  Lines         899     907      +8     
========================================
+ Hits          792     800      +8     
  Misses        107     107

Impacted Files	Coverage Δ
src/make_parameters.jl	98.12% <100%> (+0.04%)	⬆️
src/dBdt.jl	100% <100%> (ø)	⬆️

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[coveralls]

Coverage increased (+0.1%) to 88.203% when pulling f829e54 on densitydep_mortality into 21b9ff3 on next.