should offer user the option to receive SMS verification code even if the user has Telegram installed on some devices

[SmartLayer]

This was inspired by https://github.com/ars3niy/tdlib-purple/issues/113 and is an already-existing feature in Telegram Desktop.

Reasons the user might want to receive SMS instead of Telegram verification code:

1. The user installed tdlib because he lost the previous device and is using a new one, hence he couldn't receive the code from previous device anyway;
2. A mal-function lead to the telegram on previous devices not showing the verification code, as is the case in #113

In Telegram Desktop, the user is offered with the choice of receiving SMS code

In tdlib, SMS code is only activated (seemingly) after failing the Telegram code and wait out another day, as I observed when I filed #113