Added comments and help commands to user apps

Makefile

@@ -225,8 +225,8 @@ QEMUGDB = $(shell if $(QEMU) -help | grep -q '^-gdb'; \
 	then echo "-gdb tcp::$(GDBPORT)"; \
 	else echo "-s -p $(GDBPORT)"; fi)
 ifndef CPUS
-#CPUS := 2
-CPUS := 1 # For debugging
+CPUS := 2
+#CPUS := 1 # For debugging
 endif
 QEMUOPTS = -drive file=fs.img,index=1,media=disk,format=raw -drive file=xv6.img,index=0,media=disk,format=raw -smp $(CPUS) -m 512 $(QEMUEXTRA)