CHARTER: s12(c): formalise charter versions and changelog

[cyphar]

We have version numbers (and a changelog) in the Charter, so we should probably actually enshrine that in the Charter. In addition, clean up the changelog format so that it's easier to understand.

This change does introduce new requirements for the editors of the Charter, but it simply mirrors the current convention applied to Charter amendments.

In addition, define the concept of a "draft Charter version" so that we can make iterative changes to the charter through separate PRs without having to enact each minor change separately.

Split off from #86. Signed-off-by: Aleksa Sarai [email protected]

[SteveLasker]

Ok, so much for accidental clicking. Where's the undo?

[jdolitsky]

@cyphar - can you rebase/fix conflicts?