(bug 46499) Moderation bar is not displaying existence of a note

* Purge caches after adding a log note (otherwise this change was not being picked up)
* Add a indicative "Note added" message to inform people if there's additional comments for the last moderation (because the activity log is most often used to read the note, not to see the full activity history)
* After adding a note, re-render and replace the HTML, instead of adding (duplicate) logic in javascript
* Reload feedback entry even if flagging failed and display error message why it failed
* Set 255-char max length on note input field (DB will only save varchar(255) se we were truncating already)
* When pressing enter on flyout (= submitting form), stop default behavior and run tipsyCallback

Meanwhile also:
* Fix incorrect memc keys in purge script

Bug: 46499
Change-Id: I3d7a308dab24f5fc364ed2eb371efc3651c8e356
Merge "(bug 46499) Moderation bar is not displaying existence of a note"