New Navigation & Pathfinding support for 2D

-Added Navigation & NavigationPolygon nodes
-Added corresponding visual editor
-New pathfinding algorithm is modern and fast!
-Similar API to 3D Pathfinding (more coherent)

tools/editor/plugins/navigation_polygon_editor_plugin.h

@@ -0,0 +1,91 @@
+#ifndef NAVIGATIONPOLYGONEDITORPLUGIN_H
+#define NAVIGATIONPOLYGONEDITORPLUGIN_H
+
+
+
+#include "tools/editor/editor_plugin.h"
+#include "tools/editor/editor_node.h"
+#include "scene/2d/navigation_polygon.h"
+#include "scene/gui/tool_button.h"
+#include "scene/gui/button_group.h"
+
+/**
+	@author Juan Linietsky <reduzio@gmail.com>
+*/
+class CanvasItemEditor;
+
+class NavigationPolygonEditor : public HBoxContainer {
+
+	OBJ_TYPE(NavigationPolygonEditor, HBoxContainer );
+
+	UndoRedo *undo_redo;
+	enum Mode {
+
+		MODE_CREATE,
+		MODE_EDIT,
+
+	};
+
+	Mode mode;
+
+	ToolButton *button_create;
+	ToolButton *button_edit;
+
+	ConfirmationDialog *create_nav;
+
+	CanvasItemEditor *canvas_item_editor;
+	EditorNode *editor;
+	Panel *panel;
+	NavigationPolygonInstance *node;
+	MenuButton *options;
+
+	int edited_outline;
+	int edited_point;
+	Vector2 edited_point_pos;
+	DVector<Vector2> pre_move_edit;
+	Vector<Vector2> wip;
+	bool wip_active;
+
+
+	void _wip_close();
+	void _canvas_draw();
+	void _create_nav();
+
+	void _menu_option(int p_option);
+
+protected:
+	void _notification(int p_what);
+	void _node_removed(Node *p_node);
+	static void _bind_methods();
+public:
+
+	Vector2 snap_point(const Vector2& p_point) const;
+	bool forward_input_event(const InputEvent& p_event);
+	void edit(Node *p_collision_polygon);
+	NavigationPolygonEditor(EditorNode *p_editor);
+};
+
+class NavigationPolygonEditorPlugin : public EditorPlugin {
+
+	OBJ_TYPE( NavigationPolygonEditorPlugin, EditorPlugin );
+
+	NavigationPolygonEditor *collision_polygon_editor;
+	EditorNode *editor;
+
+public:
+
+	virtual bool forward_input_event(const InputEvent& p_event) { return collision_polygon_editor->forward_input_event(p_event); }
+
+	virtual String get_name() const { return "NavigationPolygonInstance"; }
+	bool has_main_screen() const { return false; }
+	virtual void edit(Object *p_node);
+	virtual bool handles(Object *p_node) const;
+	virtual void make_visible(bool p_visible);
+
+	NavigationPolygonEditorPlugin(EditorNode *p_node);
+	~NavigationPolygonEditorPlugin();
+
+};
+
+
+#endif // NAVIGATIONPOLYGONEDITORPLUGIN_H