Config - defaults

- Config is now providing a default set of all configuration variables.
- The default set is used to both initialize a Config object, and to
  create a sample .taskrc.

src/command.cpp

@@ -606,7 +606,6 @@ int handleConfig (std::string &outs)
   }
 
   out << context.config.checkForDeprecatedColor ();
-  out << context.config.checkForDuplicates ();
   // TODO Check for referenced but missing theme files.
   // TODO Check for referenced but missing string files.