Notify battery level every 10 minutes when connected to a BLE host.

Refactor battery percent : only use uint8_t to store the battery % remaining.

src/components/ble/BatteryInformationService.h

@@ -17,7 +17,7 @@ namespace Pinetime {
       void Init();
 
       int OnBatteryServiceRequested(uint16_t connectionHandle, uint16_t attributeHandle, ble_gatt_access_ctxt* context);
-
+      void NotifyBatteryLevel(uint16_t connectionHandle, uint8_t level);
     private:
       Controllers::Battery& batteryController;
       static constexpr uint16_t batteryInformationServiceId {0x180F};