Add @certainty and @normal attribute to coverage

[caseyedavis12]

I also suggested these new attributes for pbcoreAssetDate. The @Normal attribute would allow us to put the date or date range in the iso8601 format as an attribute to coverage and pbcoreAssetDate, while being able to display to the user the date in a more human-readable format.

The @certainty attribute would allow us to convey the degree of certainty of a date or date range. Values could include "circa," "approximate," etc.

[AllisonAnn]

Casey - Could you supply an example for this? I'm just not visualizing what this would look like in an XML record.

[caseyedavis12]

April 12, 1985 ? June 25, 1985 Temporal