Be more lenient about Extra field values than citeproc-js

Allow fields like "Original Date: 2018" and convert them to
"original-date: 2018" when sending to citeproc-js.

For reference:

http://citeproc-js.readthedocs.io/en/latest/csl-json/markup.html#cheater-syntax-for-odd-fields

test/tests/citeTest.js

@@ -0,0 +1,25 @@
+describe("Zotero.Cite", function () {
+	describe("#extraToCSL()", function () {
+		it("should convert Extra field values to the more restrictive citeproc-js cheater syntax", function () {
+			var str1 = 'Original Date: 2017\n' // uppercase/spaces converted to lowercase/hyphens
+				+ 'Archive-Place: New York\n' // allow hyphen even with title case
+				+ 'Container title: Title\n' // mixed case
+				+ 'DOI: 10.0/abc\n' // certain fields are uppercase
+				+ 'Archive Location: Foo\n' // requires an underscore
+				+ 'Original Publisher Place:  London, UK\n' // extra space OK
+				+ '\n\n'
+				+ "Ignore other strings: they're not fields\n"
+				+ 'This is just some text.'
+			var str2 = 'original-date: 2017\n'
+				+ 'archive-place: New York\n'
+				+ 'container-title: Title\n'
+				+ 'DOI: 10.0/abc\n'
+				+ 'archive_location: Foo\n'
+				+ 'original-publisher-place:  London, UK\n'
+				+ '\n\n'
+				+ "Ignore other strings: they're not fields\n"
+				+ 'This is just some text.';
+			assert.equal(Zotero.Cite.extraToCSL(str1), str2);
+		});
+	});
+});