Bug #804 - URL link and break line

- Addressed bug #804 by allowing rc.hyphenate to control whether hyphens are
  inserted when long lines are broken.  This may help prevent xterm from
  mis-parsing URLs in task annotations, when wrapped (thanks to Yann Davin).
- Added unit tests.

src/columns/ColString.h

@@ -45,6 +45,7 @@ public:
   void render (std::vector <std::string>&, const std::string&, int, Color&);
 
 private:
+  bool _hyphenate;
 };
 
 #endif