Create new TMX maps in your project, and edit them with Tiled from ATCS

!! Also, "created" elements show the "unsaved" asterisk in their
description until they're saved to disk. 
Added a button to the spritesheet editor to open image in an external
tool too. This may or may not remain in the app.

src/com/gpl/rpg/atcontentstudio/model/Project.java

@@ -850,6 +850,34 @@ public class Project implements ProjectTreeNode, Serializable {
 		}
 	}
 	
+	/**
+	 * 
+	 * @param node. Before calling this method, make sure that no other map with the same id exist in either created or altered.
+	 */
+	public void createElement(TMXMap node) {
+		node.writable = true;
+		if (getMap(node.id) != null) {
+			GameDataElement existingNode = getMap(node.id);
+			for (GameDataElement backlink : existingNode.getBacklinks()) {
+				backlink.elementChanged(existingNode, node);
+			}
+			existingNode.getBacklinks().clear();
+			node.writable = true;
+			node.tmxFile = new File(alteredContent.baseFolder, node.tmxFile.getName());
+			node.parent = alteredContent.gameMaps;
+			alteredContent.gameMaps.addMap(node);
+			node.link();
+			node.state = GameDataElement.State.created;
+		} else {
+			node.tmxFile = new File(createdContent.baseFolder, node.tmxFile.getName());
+			node.parent = createdContent.gameMaps;
+			createdContent.gameMaps.addMap(node);
+			node.link();
+			node.state =  GameDataElement.State.created;
+		}
+		fireElementAdded(node, getNodeIndex(node));
+	}
+	
 
 	public void moveToCreated(JSONElement target) {
 		target.childrenRemoved(new ArrayList<ProjectTreeNode>());