Display Backlight: automatically adjust to ambient sensor reading

This registers a Task, reading the ambient light sensor and adjusting the display backlight accordingly

fixes #95

epicardium/modules/brightness.c

@@ -8,18 +8,27 @@ void vAutoBrightnessTask(void *pvParameters)
 {
 	vTaskDelay(pdMS_TO_TICKS(500));
 
-	while (epic_light_sensor_run() < 0)
-		LOG_CRIT("autobrightness", "Could not start ambient sensor");
-
 	while (1) {
-		vTaskDelay(pdMS_TO_TICKS(1000));
+		vTaskDelay(pdMS_TO_TICKS(60000));
 		if (_autobrightness_enabled) {
 			unsigned short int light;
-			if (epic_light_sensor_get(&light) < 0) {
-				LOG_CRIT("autobrightness", "Could not read light sensor");
-				continue;
+
+			while (epic_light_sensor_run() < 0)
+				LOG_CRIT(
+					"autobrightness",
+					"Could not start ambient sensor"
+				);
+
+			while (epic_light_sensor_get(&light) < 0) {
+				LOG_CRIT(
+					"autobrightness",
+					"Could not read light sensor"
+				);
+				vTaskDelay(pdMS_TO_TICKS(500));
 			}
 
+			epic_light_sensor_stop();
+
 			unsigned short int brightness;
 
 			if (light > 199)