Add `verbose` setting for logging

[groenroos]

Add a verbose config value to control logging verbosity. true by default.

When set to false, all console.log and console.warns are suppressed. Added a new console.logAlways to override the suppression.

Closes #113

[codecov[bot]]

Codecov Report

Merging #523 (4f42193) into master (227d64f) will increase coverage by 0.01%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #523      +/-   ##
==========================================
+ Coverage   97.77%   97.78%   +0.01%     
==========================================
  Files          39       39              
  Lines        4769     4792      +23     
==========================================
+ Hits         4663     4686      +23     
  Misses        106      106              

Impacted Files	Coverage Δ
core/loadConfig.js	100.00% <100.00%> (ø)
lib/Cluster.js	100.00% <100.00%> (ø)

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