CRAN release v9.0.0

This release of SimInf focuses primarily on improving the functionality for performing Approximate Bayesian computation.

BREAKING CHANGES

Backwards incompatible changes that are the reason why the major version has been incremented.

• Redesigned the S4 class SimInf_abc and the interface to using the Approximate Bayesian Computation Sequential Monte Carlo ('ABC-SMC') algorithm, see the documentation for the 'abc' function. Moreover, added functionality to adaptively select a sequence of tolerances
  using the algorithm 'Adaptive Approximate Bayesian Computation Tolerance Selection' of Simola and others (2021), Bayesian Analysis.

CHANGES OR IMPROVEMENTS

• Added the function 'n_generations' to determine the number of generations in a 'SimInf_abc' object.

BUG FIXES

• The plot function for the SimInf_abc class now passes the additional arguments in '...' to the underlying plot functions.