Add INIT that works with arbitrary operators

[tkf]

No description provided.

[codecov-commenter]

Codecov Report

Merging #29 into master will increase coverage by 0.56%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #29      +/-   ##
==========================================
+ Coverage   90.00%   90.56%   +0.56%     
==========================================
  Files           2        2              
  Lines          50       53       +3     
==========================================
+ Hits           45       48       +3     
  Misses          5        5              

Impacted Files	Coverage Δ
src/InitialValues.jl	86.84% <100.00%> (+1.12%)	⬆️

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