[Tizen] Fix multiple occurrences of author in widget setting.
According to widget spec(http://www.w3.org/TR/widgets/#the-author-element-and-its-attributes), the author element's occurrences should be zero or one.
If there are more than single occurrences, just read the first one and ignore others.

BUG=XWALK-2986
Merge pull request #2640 from yejingfu/fix-widget

[Tizen] Fix multiple occurrences of author in widget setting.