load/save viewport settings

For additional smarts I save this per file. (It won't go in Filename to
let different people be looking in different areas.)

0012-on.initialize

@@ -2,6 +2,9 @@ on.initialize = function(arg)
 	if #arg > 0 then
 		Filename = arg[1]
 	end
+	if Settings[Filename] then
+		Viewport = Settings[Filename].viewport
+	end
 	if file_exists(Filename) then
 		load_graph_from_disk()
 	end

0065-on.load_settings

@@ -0,0 +1,4 @@
+on.load_settings = function(settings)
+	Settings = settings
+	-- we don't know the Filename yet, so do nothing else
+end

0066-on.save_settings

@@ -0,0 +1,5 @@
+on.save_settings = function()
+	-- save viewport by filename
+	Settings[Filename] = {viewport=Viewport}
+	return Settings
+end

0067-Settings

@@ -0,0 +1 @@
+Settings = {}