Code Cleanup

- Broke out the guts of handleCustomReport into runCustomReport, so
  that the next report can generate it's own task list, then allow the
  custom report handling to render it.  This means the next report is
  essentially (but not quite) a custom report.

src/main.h

@@ -101,6 +101,9 @@ std::string getDueDate (Task&);
 
 // custom.cpp
 std::string handleCustomReport (const std::string&);
+std::string runCustomReport (const std::string&, const std::string&,
+                             const std::string&, const std::string&,
+                             const std::string&, std::vector <Task>&);
 
 // rules.cpp
 void initializeColorRules ();