Introduce system app

Implementation as per spec

Update DIAL version

server/system_callbacks.c

@@ -0,0 +1,40 @@
+#include <string.h>
+#include "system_callbacks.h"
+
+DIALStatus system_start(DIALServer *ds, const char *appname, const char *payload, const char* query_string,
+                        const char *additionalDataUrl, DIAL_run_t *run_id, void *callback_data) {
+
+    /* Only sleep is supported action */
+    if ((0 == query_string) || (0 != strncmp( query_string, "action=sleep", sizeof("action=sleep") - 1))) {
+        return kDIALStatusErrorNotImplemented;   // Only "sleep" is valid action
+    }
+
+    /* Look for key */
+    char *key_value;
+    if ( (key_value = strchr(query_string, '&')) == '\0' ) {
+        return kDIALStatusErrorForbidden;   // No key specified.
+    }
+
+    /* Looking for hardcoded "TEST" key */
+    *key_value++ = '\0';
+    if (0 != strncmp( key_value, "key=TEST", sizeof("key=TEST") - 1)) {
+        return kDIALStatusErrorUnauth;  // Invalid key
+    }
+
+    /* Sleep not implemented in reference implementation */
+    return kDIALStatusErrorNotImplemented;
+}
+
+DIALStatus system_hide(DIALServer *ds, const char *app_name,
+                       DIAL_run_t *run_id, void *callback_data) {
+    // Always hidden
+    return kDIALStatusHide;
+}
+
+DIALStatus system_status(DIALServer *ds, const char *appname,
+                         DIAL_run_t run_id, int* pCanStop, void *callback_data) {
+    // Always hidden
+    return kDIALStatusHide;
+}
+
+