Add support for running Lua scripts that can manipulate the tty control
lines. Script is activated automatically on connect or manually via in
session key command.
The Lua scripting feature opens up for many posibilities in the future
such as adding expect like functionality to easily and programatically
interact with the connected device.
Add --log-append option which makes tio append to any existing log file.
This also changes the default behaviour of tio from appending to
overwriting any existing log file. Now you have to use this new option
to make tio append.
