tests: added micro:bit specific test app

tests/board_microbit/Makefile

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+APPLICATION = board_microbit
+include ../Makefile.tests_common
+
+BOARD = microbit
+
+# This test application is for the BBC micro:bit only
+BOARD_WHITELIST := microbit
+
+# We want to test the microbit support module
+USEMODULE += microbit
+
+include $(RIOTBASE)/Makefile.include

tests/board_microbit/README.md

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+Background
+==========
+The BBC micro:bit board comes with its own little utility library, that makes
+some of the boards unique feature like the 5x5 LED matrix usable to RIOT.
+
+This test application is therefore specialized for only that board and its
+purpose is to test and showcase the board specific utility library.
+
+
+Expected result
+===============
+When running this application, you should see the string
+`Welcome RIOT @ micro:bit!` scrolling by on the boards LED matrix.

tests/board_microbit/main.c

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+/*
+ * Copyright (C) 2016 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     tests
+ * @{
+ *
+ * @file
+ * @brief       Test the BBC micro:bit support library
+ *
+ * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+
+#include "timex.h"
+#include "microbit.h"
+
+#define DELAY           (120 * MS_IN_USEC)
+
+int main(void)
+{
+    puts("Welcome to RIOT!\n");
+    puts("Please refer to the README.md for more information about this app\n");
+
+    microbit_matrix_init();
+
+    while (1) {
+        microbit_matrix_shift_str("Welcome RIOT @ micro:bit!", DELAY);
+    }
+
+    return 0;
+}