kjournalprint should default to storage/journal

This is an enhancement request, rather than a bug. Some of the knot utilities, such as keymgr, work with LMDB databases too, and default to storage/keys, but can take the -d option to specify an alternative KASP database.

It would be nice if kjournalprint could do the same, so that I don't have to keep providing the path to the journal on the command line. In the common case, there's just one journal per server, and it's usually in storage/journal so it's kind of annoying to have to keep typing it. Instead, if kjournalprint would use a default value (either compiled it, or read from knot.conf), then it would it simpler to use. It could of course, still take the -d option to provide the path to some other journal.