GUI: Add countdown & cancel to install auto-reboot

Provide a countdown from 5 sec for the automated reboot after install.
Include a cancel button to interrupt the process.

Change-Id: Ib5e1447918adfde45eba361c088800812b690890

data.cpp

@@ -716,6 +716,8 @@ void DataManager::SetDefaultValues()
 #endif
 	mData.SetValue("tw_gui_done", "0");
 	mData.SetValue("tw_encrypt_backup", "0");
+	mData.SetValue("tw_sleep_total", "5");
+	mData.SetValue("tw_sleep", "5");
 
 	// Brightness handling
 	string findbright;