Enhancement - annotations

- Added support for "annotate" command to annotate existing tasks.
- Bumped file format to version 3, due to the annotations.
- Added unit tests to verify that annotations work.
- Changed 'description' column everywhere to include annotations.
- Added 'description_only' column to exclude the annotations.
- Fixed bug in Table.cpp that calculated the width of multi-line
  columns by using the cell length, instead of the length of the
  longest individual line.
- Updated documentation with new feature.
- Updated documentation with new column.
- Enhanced t.t unit tests to cover format 43

src/T.h

@@ -56,6 +56,7 @@ public:
 
   const std::string getDescription () const            { return mDescription; }
   void setDescription (const std::string& description) { mDescription = description; }
+  int getAnnotationCount () const                     { return mAnnotations.size (); }
 
   void getSubstitution (std::string&, std::string&) const;
   void setSubstitution (const std::string&, const std::string&);
@@ -77,6 +78,9 @@ public:
   void removeAttribute (const std::string&);
   void removeAttributes ();
 
+  void getAnnotations (std::map <time_t, std::string>&);
+  void addAnnotation (const std::string&);
+
   const std::string compose () const;
   const std::string composeCSV ();
   void parse (const std::string&);
@@ -93,9 +97,9 @@ private:
   std::vector<std::string>           mTags;
   std::vector<std::string>           mRemoveTags;
   std::map<std::string, std::string> mAttributes;
-
   std::string                        mFrom;
   std::string                        mTo;
+  std::map <time_t, std::string>     mAnnotations;
 };
 
 #endif