AUI-1358 - Make aui-progressbar accessible

Hi Marc,

Attached is an update for https://issues.liferay.com/browse/AUI-1358.

I had to make some changes affecting the Aria plugin.  It was actually kinda messed up before this.  Chromevox would crash on the first progress bar for me.  It should be alright now though.

Please let me know if there are any issues.

Thanks!