Add --build command

First pass at the build system described in #356.

To test it, move to a new, empty directory and try `tiddlywiki
editions/tw5.com --verbose --build`

core/modules/commands/clearpassword.js

@@ -0,0 +1,33 @@
+/*\
+title: $:/core/modules/commands/clearpassword.js
+type: application/javascript
+module-type: command
+
+Clear password for crypto operations
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+exports.info = {
+	name: "clearpassword",
+	synchronous: true
+};
+
+var Command = function(params,commander,callback) {
+	this.params = params;
+	this.commander = commander;
+	this.callback = callback;
+};
+
+Command.prototype.execute = function() {
+	$tw.crypto.setPassword(null);
+	return null;
+};
+
+exports.Command = Command;
+
+})();