This refactors and fixes unicode issues where entities don't display
properly due to being a special character that seems to be rendered
incorrectly in a non-deterministic way every time.
This either removes aria-hidden=true assignments from buttons with
text, or adds a span to only hide the 'x' symbol rather than the
button for closing buttons.
Fixes#268.
Modified significantly by tabbott to:
* improve code cleanliness / repetition
* add missing translation tags
* move code into message_edit.js
* correspond with the new backend.
* not display the option for messages only topic-edited
Brock Whittaker
Vaida Plankyte
aakash-cr7
Cynthia Lin
adnrs96
Kartik Maji