Prova v2.0.0

• The argument learnt =, common to many functions, has been changed to K = for brevity. Previous "learnt" objects can still be used with the K = argument.
• The functions flexiplot() and plotquantiles() are replaced by the single function pplot(); argument type = 'qx' reproduces the usage of plotquantiles().
• Fixed a bug that prevented use of pre-existing parallel cluster.
• print() now prints correctly "probability" objects generated by qPr().
• Metadata object meta_penguins for the R dataset datasets::penguins is now included in the package.
• Included a minimal example in the README.
• Rewrite of some internal code.