Adjusting debug_print_plan to be more useful by default

Back in April we changed EXPLAIN VERBOSE to not dump the internal plan
tree anymore, on the grounds that non-hackers didn't want that info and
hackers could get it with debug_print_plan and related variables.
Well, now that I've tried to do some planner development work relying on
debug_print_plan instead of EXPLAIN VERBOSE, I find it a mite annoying.
It's not sufficient to set debug_print_plan = true, because the output
comes out at priority DEBUG1, which is to say it doesn't come out at all
in a default configuration. If you boost up client_min_messages or
log_min_messages so you can see it, you get lots of extraneous debugging
messages too.

I'd like to propose that the messages emitted by debug_print_plan
and friends be given priority LOG rather than DEBUG1. If you've gone
to the trouble of turning on the variable, then you presumably want the
results, so it seems dumb to print them at a priority that isn't logged
by default. (Note that this is biased to the assumption that you want
the messages in the postmaster log, not on the console. Which is
usually what I want, but maybe someone wants to argue for NOTICE?)

I'd also like to propose making debug_pretty_print default to ON.
At least for me, the other formatting is 100% unreadable.

Comments?

regards, tom lane