renamed protocol methods to reflect the new module name

main.c

@@ -37,7 +37,7 @@
 
 int main(void)
 {
-  sp_init();        
+  protocol_init();        
   settings_init();  
   plan_init();      
   st_init();        
@@ -46,7 +46,7 @@ int main(void)
                     
   for(;;){
     sleep_mode(); // Wait for it ...
-    sp_process(); // ... process the serial protocol
+    protocol_process(); // ... process the serial protocol
   }
   return 0;   /* never reached */
 }