Initial commit of changes for 1.2.3. This includes:

- Scripting support: Allows for recording and playback of mouse/keyboard input and various system control actions.  Simple (i.e. basic) scripting format.

- Fix for stale packets left in ethernet input queue; packets received by pcap while Alto's receiver is off are discarded.

- Mouse input made more accurate, and tweaked to avoid Alto microcode bug that causes erroneous mouse inputs under very rare circumstances on real hardware, but much more frequently under emulation.

- Small code cleanup here and there.  Moved many UI strings to resources, many more to go.

Contralto/SdlUI/DebuggerPrompt.cs

@@ -16,6 +16,7 @@
 */
 
 
+using Contralto.Scripting;
 using System;
 using System.Collections.Generic;
 using System.Text;