Create new event handlers: Settings.Load, Settings.Save and Settings.Done

Extract code for loading/saving tty-related settings from src/setup.c
to apropriate event handlers into lib/tty module

Signed-off-by: Slava Zanko <slavazanko@gmail.com>
Move pending_keys code to different function

Signed-off-by: Slava Zanko <slavazanko@gmail.com>
Add handling of Mouse.extended_protocol setting.

Possible values is: 1006 and 1015.
Default value: 1006

Signed-off-by: Slava Zanko <slavazanko@gmail.com>
Add support for SGR-1006 mouse protocol.

Signed-off-by: Slava Zanko <slavazanko@gmail.com>