deep clone $values

[mb706]

fixes #272

[mb706]

Using the default clone method of R6 objects on the $values slot now

[codecov-io]

Codecov Report

Merging #273 into master will increase coverage by 0.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #273      +/-   ##
==========================================
+ Coverage   95.16%   95.21%   +0.05%     
==========================================
  Files          20       20              
  Lines         496      502       +6     
==========================================
+ Hits          472      478       +6     
  Misses         24       24              

Impacted Files	Coverage Δ
R/ParamSet.R	97.38% <100.00%> (+0.10%)	⬆️

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