Make 'Mutator' class easier to extend

[jenetics]

Currently, the Mutator class allows you to override on protected method for implementing own mutators:

protected int mutate(final MSeq<G> genes, final double p);

This method allows to change the genes of one chromosome, where the chromosome can't be chosen by the implementor. The second drawback is, that it is not possible to change the length of the Chromosome and Genotype.

To reach the desired flexibility, the signature of the existing method is changed and an additional is added:

// Using a 'List' instead of a 'MSeq' also allows to chromosome length.
protected int mutateChromosome(final List<G> chromosome, final double p);

// The additional method allows to change the genotype, including it's length.
protected int mutateGenotype(final List<Chromosome<G>> genotype, final double p);

This is an incompatible change.

[jenetics]

The Mutator class can now be extended through four methods:

protected MutatorResult<Phenotype<G, C>> mutate(
	final Phenotype<G, C> phenotype,
	final long generation,
	final double p,
	final Random random
)

protected MutatorResult<Genotype<G>> mutate(
	final Genotype<G> genotype,
	final double p,
	final Random random
)

protected MutatorResult<Chromosome<G>> mutate(
	final Chromosome<G> chromosome,
	final double p,
	final Random random
)

protected G mutate(final G gene, final Random random)

[jenetics]

Merged into r4.0.0 branch.