listconfigs is convenient, but it doesn't handle multi-options well: it
outputs an object with duplicate fields in this case (e.g. log-file), nor
is it extensible to show more than raw values.
However, listconfigs doesn't do what other list commands do (use a
sub-object "configs") so we can put the new values under that.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: JSON-RPC: `listconfigs` now has `configs` subobject with more information about each config option.
b9270c564a