Moved error reporting to ScreenSystemLayer error.lua.  ScreenSystemLayer overlay/default.lua restored to previous.  Error messages are now broadcast with the ScriptError message instead of SystemMessage.  Added show/hide error messages toggle and clear error messages to debug menu.  Nuked ScreenConsoleOverlay for being unfinished and duplicating ScreenSystemLayer.  Changed Actor:tween and Tween::CreateFromStack to use ReportScriptError on invalid tween params.  Changed some OptionRowList things to use ReportScriptError on invalid metrics.