GUI for --disable-wallet compiles and -disablewallet mode

There is not much in the GUI to be done without wallet,
though it's possible to change options, watch the sync process,
and use the debug console.

So embed the debug console in the main window.

configure.ac

@@ -567,9 +567,6 @@ if test x$bitcoin_enable_qt != xno; then
       AC_MSG_ERROR("QT Test lib not found. Use --disable-tests or --without-qt.")
     fi
   fi
-  if test x$enable_wallet == xno; then
-    AC_MSG_ERROR([Cannot currently build Qt GUI with wallet disabled. Use --without-qt.])
-  fi
 fi
 
 if test x$use_tests = xyes; then