rl_helper: restore terminal settings on exit

We disable echo on terminal, so we need to restore any changes that we
made.
Test for EOF on getchar

If something gone wrong reading char, we need to break main loop.
rl_helper: handle ctrl-c command

When user press the sequence ctrl-c, we can handle it changing terminal
settings to raw. So we can do a smooth exit.
Check if it's running as root user

Trying to enable bluetooth module without root permission, give us some
weird issues, it does not work. So we need to check it before doing
anything.