change screen into a periodictask, so it can be used with the scheduler

src/screen.h

@@ -1,11 +1,10 @@
 #pragma once
 
+#include "PeriodicTask.h"
+
 void screen_print(const char * text);
 
-/// @return how many msecs can we sleep before we want service again
-uint32_t screen_loop();
-
-void screen_setup(), screen_on(), screen_off(), screen_press();
+void screen_on(), screen_off(), screen_press();
 
 // Show the bluetooth PIN screen
 void screen_start_bluetooth(uint32_t pin); 
@@ -14,3 +13,20 @@ void screen_start_bluetooth(uint32_t pin);
 void screen_set_frames();
 
 bool is_screen_on();
+
+/**
+ * Slowly I'm moving screen crap into this class
+ */
+class Screen : public PeriodicTask
+{
+public:
+
+    void setup();
+
+    virtual void doTask();
+
+    /// Turn on the screen asap
+    void doWakeScreen();
+};
+
+extern Screen screen;