bitcoind should fail or at least warn when encountering an option it doesn't understand #2427

Pass a fake option to bitcoind, whether on the command line or in the bitcoin.conf file. I would expect the daemon to fail to start, or at least warn you about the option it doesn't understand. Instead, it silently ignores the option and runs normally. This makes it unnecessarily difficult to debug configuration issues. For example, an option may not be compatible with your version of bitcoind, or you may have misspelled something.

I would prefer that it output a warning to debug.log rather than stdout or stderr.

Dupliate of #1044