LPS-49486 - 508 Compliance for Documents and Media - Ratings

Hi Jon,

Attached is an update for https://issues.liferay.com/browse/LPS-49486.

@natecavanaugh recommended that I take advantage of the 'hide-accessible' class to allow tabbing into the hidden rating stars.

In order to limit the scope of this change to just the document library, I added an attribute ('hoverVoteAccessible') to the ratings taglib.  I'm not sure if that is the best approach since this is the only area in portal where it is used. 

Please let me know if there are any issues.

Thanks!