add PID file handling to clients (including signal handling to remove the files)

clients/lcdproc/lcdproc.conf

@@ -17,6 +17,9 @@ ReportToSyslog=false
 # run in foreground [default: false; legal: true, false]
 #Foreground=true
 
+# PidFile location when running as daemon [default: /var/run/lcdproc.pid]
+#PidFile=/var/run/lcdproc.pid
+
 # slow down initial announcement of modes (in 1/100s)
 #delay=2