[Public API Reform] Is it useful to edit candidate name with history. Should be immutable?

[julien-boudry]

Context

Candidate name can be edited at any time. Full history and checksum are conserved and computed.
It's a really complex mechanism (to understand, for the project code), a source of confusion, and neither is used in practice.

Change vote is also complex but more useful for voting simulations.

Proposal

Candidates objects should be immutable.
Should be coupled with a new API to remove Candidates from an Election, and add Candidates after Vote (also complex actually).

Breaking changes

No more name changes, no more history.