get_input_* everywhere

Scheme layer used: 68

For some reason, Telegram doesn't have enough with the InputPeer. There also exist InputChannel and InputUser! You don't have to worry about those anymore, it's handled internally now.

Besides this, every Telegram object now features a new default .__str__ look, and also a .stringify() method to pretty format them, if you ever need to inspect them.

The library now uses the DEBUG level everywhere, so no more warnings or information messages if you had logging enabled.

The no_webpage parameter from .send_message has been renamed to link_preview for clarity, so now it does the opposite (but has a clearer intention).