bitbake: event.py, knotty.py, ncurses.py, runningbuild.py: Add support for LogExecTTY...

bitbake: event.py, knotty.py, ncurses.py, runningbuild.py: Add support for LogExecTTY event

The LogExecTTY even is intended to provide the ability to spawn a task
on a the controlling tty, if a tty is availble.  When a controlling
tty is not availble the previous behavior is preserved where a warning
is issued about the action an end user must execute.

All the available UI's were tested against the new event type.

This feature is primarily intended for hooking up a screen client
session automatically on the controlling tty to allow for a more
streamlined end user experience when using a pure command line driven
environment.  The changes that send the LogExecTTY event are in the
oe-core side.

(Bitbake rev: cffe80d82a46aaf52ff4a7b6409435754043553f)

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>