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/task.cpp

@@ -88,6 +88,10 @@ static std::string shortUsage (Config& conf)
   table.addCell (row, 1, "task append [tags] [attrs] desc...");
   table.addCell (row, 2, "Appends more description to an existing task");
 
+  row = table.addRow ();
+  table.addCell (row, 1, "task annotate ID desc...");
+  table.addCell (row, 2, "Adds an annotation to an existing task");
+
   row = table.addRow ();
   table.addCell (row, 1, "task completed [tags] [attrs] desc...");
   table.addCell (row, 2, "Chronological listing of all completed tasks matching the specified criteria");
@@ -759,12 +763,12 @@ void updateShadowFile (TDB& tdb, Config& conf)
 
   catch (std::string& error)
   {
-    std::cout << error << std::endl;
+    std::cerr << error << std::endl;
   }
 
   catch (...)
   {
-    std::cout << "Unknown error." << std::endl;
+    std::cerr << "Unknown error." << std::endl;
   }
 }
 
@@ -833,6 +837,7 @@ std::string runTaskCommand (
   else if (command == "" && task.getId ())  { cmdMod = true; out = handleModify   (tdb, task, conf); }
   else if (command == "add")                { cmdMod = true; out = handleAdd      (tdb, task, conf); }
   else if (command == "append")             { cmdMod = true; out = handleAppend   (tdb, task, conf); }
+  else if (command == "annotate")           { cmdMod = true; out = handleAnnotate (tdb, task, conf); }
   else if (command == "done")               { cmdMod = true; out = handleDone     (tdb, task, conf); }
   else if (command == "undelete")           { cmdMod = true; out = handleUndelete (tdb, task, conf); }
   else if (command == "delete")             { cmdMod = true; out = handleDelete   (tdb, task, conf); }