Display brightness support (#26)

* cleanup

* brightness control and app

* cleanup

* persistant storage of display settings

* fix for missing include

* header cleanup

* fix pc build

* add docs

* move display app to tactility project

boards/yellow_board/bootstrap.c

@@ -1,6 +1,6 @@
 #include "config.h"
-#include "kernel.h"
-#include "log.h"
+#include "tactility_core.h"
+#include "display_i.h"
 #include <driver/spi_common.h>
 
 #define TAG "twodotfour_bootstrap"
@@ -83,5 +83,12 @@ bool twodotfour_bootstrap() {
         return false;
     }
 
+    // Don't turn the backlight on yet - Tactility init will take care of it
+    TT_LOG_I(TAG, "Init backlight");
+    if (!twodotfour_backlight_init()) {
+        TT_LOG_E(TAG, "Init backlight failed");
+        return false;
+    }
+
     return true;
 }