This commit removes the private network initialization logic from NSH and puts in a common location at apps/netutils/netinit. Now that netork initialization logic can be used by applications that do not include NSH.

Squashed commit of the following:

    apps/nshlib:  Remove NSH initialization.  Now uses the common apps/netutils/netinit logic (which was cloned from nshlib to begin with).

    apps/netutils/netinit:  Clone network initialization logic from NSH to this directory so that it can be available for general use.

nshlib/nsh_init.c

@@ -42,6 +42,7 @@
 #include <sys/boardctl.h>
 
 #include "system/readline.h"
+#include "netutils/netinit.h"
 #include "nshlib/nshlib.h"
 
 #include "nsh.h"
@@ -103,7 +104,9 @@ void nsh_initialize(void)
   (void)boardctl(BOARDIOC_INIT, 0);
 #endif
 
+#ifdef CONFIG_NSH_NETINIT
   /* Bring up the network */
 
-  (void)nsh_netinit();
+  (void)netinit_bringup();
+#endif
 }