Separate the PDF parser from the image parser

It was a bit of a hack, and made it harder to customise PDF presentation

core/modules/parsers/pdfparser.js

@@ -0,0 +1,33 @@
+/*\
+title: $:/core/modules/parsers/pdfparser.js
+type: application/javascript
+module-type: parser
+
+The PDF parser embeds a PDF viewer
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+var ImageParser = function(type,text,options) {
+	var element = {
+			type: "element",
+			tag: "embed",
+			attributes: {}
+		},
+		src;
+	if(options._canonical_uri) {
+		element.attributes.src = {type: "string", value: options._canonical_uri};
+	} else if(text) {
+		element.attributes.src = {type: "string", value: "data:application/pdf;base64," + text};
+	}
+	this.tree = [element];
+};
+
+exports["application/pdf"] = ImageParser;
+
+})();
+