Fixed an issue with duplicate tag keys when counting todo tah matches
and ongoing work on matching continuous lines of tags.
Debug todo.
Initial draft work on the task-todo(7) unit tests and work on migrating
to : $((increment++)) style syntax rather than ((increment++)) syntax
which was causing bash(1) to quit under some situations.
Ensured that all increment and decrement operations are :
$((increment++)) syntax.