Bug Fix, Tweaks

- .taskrc debug= now defaults to 'off', which will reduce clutter
  and won't surprise beta testers.
- interactive.cpp did not compile when ncurses was not detected by
  autoconf.  That code branch obviously never got executed.
- The interactive shell now instructs the user to type 'quit' to
  leave the shell.

src/Context.cpp

@@ -147,7 +147,7 @@ int Context::run ()
   }
 
   // Dump all debug messages.
-  if (config.get ("debug", true))
+  if (config.get (std::string ("debug"), false))
     foreach (d, debugMessages)
       std::cout << colorizeDebug (*d) << std::endl;