Added Support for Telegram#

Telegram support has been implemented.

Now you can both create your own chatbots and operate on behalf of a Telegram account (that is, emulate a Telegram client).
Sending and receiving messages to both people and channels, downloading message history, retrieving contact list, sending and receiving photos and arbitrary files, and much more have been implemented.

To illustrate the new capabilities, we have added two new demo projects to the Projects folder of the distribution.
One demonstrates working with Telegram on behalf of a client, the other — on behalf of a chatbot.