Granular construction of McOptionsValues

Refactor in support of libqueso#569 to enable various layered
phases of constructing McOptionsValues.  This mirrors work done in
other *OptionsValues.

src/stats/inc/MonteCarloSGOptions.h

@@ -100,6 +100,15 @@ class McOptionsValues
   /*! It assigns the same options values from  \c src to \c this.*/
   McOptionsValues            (const McOptionsValues& src);
 
+  //! Set default values for parameter options
+  void set_defaults();
+
+  //! Set parameter option names to begin with prefix
+  void set_prefix(const std::string& prefix);
+
+  //! Given prefix, read the input file for parameters named "prefix"+*
+  void parse(const BaseEnvironment& env, const std::string& prefix);
+
   //! Destructor
   virtual ~McOptionsValues            ();
   //@}
@@ -141,7 +150,7 @@ class McOptionsValues
 
 private:
 #ifndef QUESO_DISABLE_BOOST_PROGRAM_OPTIONS
-  BoostInputOptionsParser * m_parser;
+  ScopedPtr<BoostInputOptionsParser>::Type m_parser;
 #endif  // QUESO_DISABLE_BOOST_PROGRAM_OPTIONS
 
   std::string                   m_option_help;