Add salted version of sampler functions in EXPRESSION samplers

[pumken]

Pull Request

A slightly less naïve implementation of #371. Every sampler specified in an EXPRESSION sampler generates two functions: sampler(Point) and samplerSalted(Point, double). The salted version requires an additional, mandatory argument for salt, per Astrash's recommendation.

May require a documentation change to record the existence of this feature and to warn against duplication of function names. Though highly unlikely, this change breaks config packs that result in name duplication.

The previous PR was closed so that the git history can be made cleaner without the need for revert commits.

Again open for any feedback at all.

Closes #371.

Changelog

• Add additional salted version of samplers in EXPRESSIONs.

Checklist

Mandatory checks

• The base branch of this PR is an unreleased version branch (that has a ver/ prefix)
  or is a branch that is intended to be merged into a version branch.
• There are no already existing PRs that provide the same changes.
• The PR is within the scope of Terra (i.e. is something a configurable terrain generator should be doing).
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  document in the root of the git repository.

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• Introduces a breaking change
• Introduces new functionality in a backwards compatible way.
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Documentation

• My change requires a change to the documentation.
• I have updated the documentation accordingly.

Testing

• I have added tests to cover my changes.
• All new and existing tests passed.

Licensing

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  release it under GPLv3.
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  released under GPLv3 or a compatible license.

[duplexsystem]

Looks good to me