tests: add test for veml6070 sensor

tests/driver_veml6070/Makefile

+APPLICATION = driver_veml6070
+include ../Makefile.tests_common
+
+USEMODULE += veml6070
+USEMODULE += xtimer
+
+include $(RIOTBASE)/Makefile.include

tests/driver_veml6070/Readme.md

+## About
+This is a test application for the VEML6070 UV sensor.
+
+## Usage
+The application initializes the VEML6070 sensor and displays the UV indice
+measure every 2 seconds.

tests/driver_veml6070/main.c

+/*
+ * Copyright (C) 2017 Inria
+ *
+ * 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 application for the VEML6070 UV sensor
+ *
+ * @author      Alexandre Abadie <alexandre.abadie@inria.fr>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+#include <inttypes.h>
+
+#include "veml6070.h"
+#include "veml6070_params.h"
+#include "xtimer.h"
+#include "board.h"
+
+#define SLEEP_2S   (2 * 1000 * 1000u) /* 2 seconds delay between printf */
+
+int main(void)
+{
+    veml6070_t dev;
+    int result;
+
+    puts("VEML6070 test application\n");
+
+    printf("+------------Initializing------------+\n");
+    result = veml6070_init(&dev, &veml6070_params[0]);
+    if (result == VEML6070_ERR_I2C) {
+        puts("[Error] The given i2c is not enabled");
+        return 1;
+    } else {
+        printf("Initialization successful\n\n");
+    }
+
+    printf("\n+--------Starting Measurements--------+\n");
+    while (1) {
+        printf("UV indive: %d"
+               "\n+-------------------------------------+\n",
+               veml6070_read_uv(&dev));
+
+        xtimer_usleep(SLEEP_2S);
+    }
+
+    return 0;
+}