atddiff: Add --backward, --forward, --types filters

[mjambon]

Closes #365

PR checklist

• [x] New code has tests to catch future regressions
• [x] Documentation is up-to-date
• [x] CHANGES.md is up-to-date

[mjambon]

I'm merging this to minimize conflicts but let know if there's anything I should revise on this or other PRs that were merged quickly.

I'm planning to make another atd release this week.