Extend new parser mechanism to determine parser based on content type

And add an image parser and a plain text parser

core/modules/parsers/textparser.js

@@ -0,0 +1,31 @@
+/*\
+title: $:/core/modules/parsers/textparser.js
+type: application/javascript
+module-type: newparser
+
+The plain text parser processes blocks of source text into a degenerate parse tree consisting of a single text node
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+var TextParser = function(type,text,options) {
+	this.tree = [{
+		type: "element",
+		tag: "pre",
+		children: [{
+			type: "text",
+			text: text
+		}]
+	}];
+};
+
+exports["text/plain"] = TextParser;
+exports["text/html"] = TextParser;
+exports["application/javascript"] = TextParser;
+
+})();
+