Iconfont icons are of no value to screenreader users; in our case,
they get alternative text. By adding 'aria-hidden="true"' to the
<span> holding the iconfont icon, we avoid the screenreader trying
to announce the iconfont icon.
This commit is to ensure consistency with the core across the
additional_plugins repository. While I was at it, I also cleaned
up the ChangeLogs, trying to establish a common pattern.
