Add support for JSON files containing a single tiddler

At the moment, we support JSON files containing an array of tiddlers.
With this change the core will import files containing a single
tiddler. Also adding templates for saving individual tiddlers in JSON
format

boot/boot.js

@@ -1320,8 +1320,8 @@ $tw.modules.define("$:/boot/tiddlerdeserializer/html","tiddlerdeserializer",{
 });
 $tw.modules.define("$:/boot/tiddlerdeserializer/json","tiddlerdeserializer",{
 	"application/json": function(text,fields) {
-		var tiddlers = JSON.parse(text);
+		var data = JSON.parse(text);
-		return tiddlers;
+		return $tw.utils.isArray(data) ? data : [data];
 	}
 });
 

core/modules/deserializers.js

@@ -82,7 +82,9 @@ exports["application/json"] = function(text,fields) {
 			text: ""
 		}]
 	}
-	if($tw.utils.isArray(incoming)) {
+	if(!$tw.utils.isArray(incoming)) {
+		incoming = [incoming];
+	}
 	for(var t=0; t<incoming.length; t++) {
 		var incomingFields = incoming[t],
 			fields = {};
@@ -93,7 +95,6 @@ exports["application/json"] = function(text,fields) {
 		}
 		results.push(fields);
 	}
-	}
 	return results;
 };
 

core/modules/macros/jsontiddler.js

@@ -0,0 +1,40 @@
+/*\
+title: $:/core/modules/macros/jsontiddler.js
+type: application/javascript
+module-type: macro
+
+Macro to output a single tiddler to JSON
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+/*
+Information about this macro
+*/
+
+exports.name = "jsontiddler";
+
+exports.params = [
+	{name: "title"}
+];
+
+/*
+Run the macro
+*/
+exports.run = function(title) {
+	title = title || this.getVariable("currentTiddler");
+	var tiddler = !!title && this.wiki.getTiddler(title),
+		fields = new Object();
+	if(tiddler) {
+		for(var field in tiddler.fields) {
+			fields[field] = tiddler.getFieldString(field);
+		}
+	}
+	return JSON.stringify(fields,null,$tw.config.preferences.jsonSpaces);
+};
+
+})();

core/templates/json-tiddler.tid

@@ -0,0 +1,7 @@
+title: $:/core/templates/json-tiddler
+
+<!--
+
+This template is used for saving tiddlers as raw JSON
+
+--><$text text=<<jsontiddler>>/>

editions/tw5.com/tiddlers/macros/jsontiddler Macro.tid

@@ -0,0 +1,13 @@
+caption: jsontiddlers
+created: 20170317140130417
+modified: 20170317140226040
+tags: Macros [[Core Macros]]
+title: jsontiddler Macro
+type: text/vnd.tiddlywiki
+
+The <<.def jsontiddler>> [[macro|Macros]] returns the fields of a single tiddler in [[JSON|JavaScript Object Notation]] form.
+
+!! Parameters
+
+;title
+: The title of a tiddler