Use best first creator for OpenURL author, not just first position

This also fixes Google Scholar Search lookup to use an author not in first creator
position [1].

[1] https://forums.zotero.org/discussion/58384/

test/tests/openurlTest.js

@@ -0,0 +1,23 @@
+"use strict";
+
+describe("Zotero.OpenURL", function() {
+	describe("#createContextObject()", function () {
+		it("should use firstCreator for author", function* () {
+			var item = createUnsavedDataObject('item');
+			item.setCreators([
+				{
+					firstName: "Aaa",
+					lastName: "Editor",
+					creatorType: 'editor'
+				},
+				{
+					firstName: "Bbb",
+					lastName: "Author",
+					creatorType: 'author'
+				}
+			]);
+			var co = Zotero.OpenURL.createContextObject(item, "1.0");
+			assert.include(co, '&rft.aufirst=Bbb&rft.aulast=Author&');
+		});
+	});
+});