Even when the config is invalid, the welcome message should be printed.

We shouldn't print this if some checks might result in immediately
closing the program.

This gives more context for the "You did not set a new PB." message that
normally appears at startup. Also, the explanation when we ignore PB.txt
now appears even when it doesn't contain a number.

This is intended to address some user confusion about what the number
represents (some people thought it had to do with the contents of the
branch and were worried about it being the same between threads) and
whether the message is important or not (some people thought that
numbers not printed had some checks being skipped and even worried that
PBs would not be found on these branches).

This prevents a fairly common problem where two log lines can end up
interleaved.

It was technically possible to perform 100,000 moves and then restart.
More realistically, this change is mainly useful if someone lowers the
default iteration limit.

The extra information about steps and frames was extremely confusing to
users and, as a pure debugging feature, was inappropriate at log level 3,
if not even at log level 6.

This was accidentally checking for the Random move selection method
instead of Manual.

Windows does not generate SIGTERM when closing a program, and it
actually doesn't support SIGINT either; it may work, but correct
behavior is not guaranteed.

Using Ctrl+Break to shut down and closing the window both resulted in
instant termination.

This check prevents now obsoleted records from being submitted, as the
thread with the actual record either already has returned or will at
some point.