Support user defined attributes
I have a UDA for "URL" that's a string. It would be nice if "task open [task_id]" could be configured to either (1) use a given UDA (in this case, "url") when called or (2) to search through the UDAs for a task and prompt the user to open any valid entries.

Knowing no Perl, this feature request will not be completed by me :), just putting the idea out there. 
