Show the following actions on the post events page:
* Post bans and unbans
* Post deletions and undeletions
* Thumbnail regenerations and IQDB regenerations
* Favorites moves
* Rating locks and unlocks
* Note locks and unlocks
Fixes#3825: Events/Moderation page for each post should show eventual ban actions
* Add a global /post_events page that shows the history of all approvals,
disapprovals, flags, appeals, and replacements on a single page.
* Redesign the /posts/:id/events page to show all approval, disapproval,
flag, appeal, and replacement events for a single post (before it only
showed approvals, flags, and appeals).
* Remove the replacement history link from the post show page. Replacements
are now included in the post events page (closes#4948: Highlighed replacements).
* Add /post_approvals/:id and /post_replacements/:id routes (these are
used by the "Details" link on the post events page).
