Support hiding comments until `Show comments' click
Support hiding comments until `Show comments' click

- Export function: Debiki.v0.showInteractionsOnClick, from debiki.js
- Add html for tagsThatHideShowInteractions: a <style> that hides
  comments, edits and the Reply button, and a <script> that shows them
  on click.
- Show comments on inline menu Reply or Edit button click

debiki/debiki-server-old,debiki/debiki-server-old,debiki/debiki-server-old,debiki/debiki-server-old