serialMenu speed-up

Changed Editor.java to add optional rescan of serial ports.
Original behavior of Tools menu would rescan serial ports every time it is opened.  This can be time consuming, especially if you have an abundance of virtual or bluetooth serial devices.  New behavior adds a check button to serialMenu to disable the automatic scanning and a button to manually scan ports.

![Arduino](https://f.cloud.github.com/assets/2180481/31524/8cde6df6-4f8e-11e2-9a78-a3adc2586591.png)