yahtzR v1.2.0

Behind the scenes, much of the gamme variation related code is now implemented
with S3 methods.

Added game variations for Yatzy and a 4 dice variation of said.

"Long straight" nor relabled as "Large straight".

Change to the argument calls for the yahtzR() function. Introduces a slight backward
incompatibility to previous releases. Apologies to my zero users...