Add a log_print() function

Something like:

    log_print(int verbosity, bool main_only, char *format, ...)

Goals: Any code that now prints to stderr and/or log with a bunch of conditions (with 3-10 lines of code each time) could be replaced with a single call to a shared function in logger.c with following options:

• Send to screen, or log, or both.
• Line-wrap at word boundary (at whatever we deem to be the output width).
• Only print to parent process, or any/all. Only print node number when applicable.
• Optionally colorize serious notes (eg. yellow) and warnings (eg. red).
• Minimum verbosity for sending to screen and a separate minimum "log level" for sending to log. BTW I think I want specific future options like --log-no-rule-details and --log-no-mode-details while --log-none would deprecate the current -nolog. Perhaps this should be considered.

I have initial code for this, but it really needs some thought to end up really good.

Start by reviewing logger.c and the existing code that prints to stderr and/or the log with conditional logic. Compare those call sites with the proposed verbosity, output-target, wrapping, process, node, color, and log-level options; done means the shared interface and its scope are settled and the relevant call sites can use it consistently.