Add RBParameters::push_back_extra_value()

Again, we already had this support for "normal" parameters, so makes
sense to add it for "extra" parameters as well.

Author: jwpeterson

include/reduced_basis/rb_parameters.h

@@ -232,6 +232,11 @@ class RBParameters
    */
   void push_back_value(const std::string & param_name, Real value);
 
+  /**
+   * Same as push_back_value(), but for "extra" parameters.
+   */
+  void push_back_extra_value(const std::string & param_name, Real value);
+
   /**
    * Get the value of the specified extra parameter, throwing an error
    * if it does not exist.

src/reduced_basis/rb_parameters.C

@@ -139,6 +139,13 @@ void RBParameters::push_back_value(const std::string & param_name, Real value)
   _parameters[param_name].push_back(value);
 }
 
+void RBParameters::push_back_extra_value(const std::string & param_name, Real value)
+{
+  // Get reference to vector of values for this extra parameter, creating it
+  // if it does not already exist, and push back the specified value.
+  _extra_parameters[param_name].push_back(value);
+}
+
 Real RBParameters::get_extra_value(const std::string & param_name) const
 {
   // Same as get_value(param_name) but for the map of extra parameters