added commands for XReceive and YReceive

git-svn-id: https://svn.inf.ethz.ch/svn/lecturers/a2/trunk@7715 8c9fc860-2736-0410-a75d-ab315db34111

source/Shell.Alias

@@ -37,3 +37,5 @@ whoimports=SystemTools.WhoImports
 lsusb=UsbInfo.Show
 ps=SystemTools.ShowProcesses
 halt=SystemTools.PowerDown
+xrecv=ShellSerial.XReceive
+yrecv=ShellSerial.YReceive