Feature #546

- Added feature #546, which is a 'count' command that counts tasks, and is
  intended to help scripts that manipulate task output.
- Added unit tests.
- Added man page description.

src/report.cpp

@@ -244,6 +244,10 @@ int shortUsage (std::string& outs)
   table.addCell (row, 2, "Displays all possible colors, a named sample, or a "
                          "legend containing all currently defined colors.");
 
+  row = table.addRow ();
+  table.addCell (row, 1, "task count [filter]");
+  table.addCell (row, 2, "Shows only the number of matching tasks.");
+
   row = table.addRow ();
   table.addCell (row, 1, "task version");
   table.addCell (row, 2, "Shows the task version number.");