Initial topology induced by a family of functions

[mkerjean]

Motivation for this change

Enhances initial_topoly.v by constructing the topology induced by a family of functions, instead of a single one.

Checklist

• added corresponding entries in CHANGELOG_UNRELEASED.md

• added corresponding documentation in the headers

Reference: How to document

Merge policy

As a rule of thumb:

• PRs with several commits that make sense individually and that
  all compile are preferentially merged into master.
• PRs with disorganized commits are very likely to be squash-rebased.

Reminder to reviewers

• Read this Checklist
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