Add file monitoring service
Add observer to monitor creating image file

CAUTION: now, this app monitor all directories of sdcard for testing so
it can provide overload to application.
Add TakenNotification and fix bug

TakenNotification is creating notification in top bar when FileObserver
capture event.
But when new file has been created by taken pictures or capture
screenshot, the file can’t be decode. So I changed monitoring options
CREATE to CLOSE_WRITE.