Enhancement - import command

- Implemented import command
- Implemented Context::clearMessages to remove all accumulated
  messages.  This is needed because parts of the import process are
  recursive and we don't want Context to dump messages for every
  import record on completion.

src/Context.h

@@ -55,10 +55,12 @@ public:
   void header (const std::string&);    // Header sink
   void message (const std::string&);   // Message sink
   void footnote (const std::string&);  // Footnote sink
+  void clearMessages ();
+
+  void parse ();
 
 private:
   void loadCorrectConfigFile ();
-  void parse ();
   void autoFilter ();
 
 public: