Ticket #69 (new enhancement)

Description

Currently, Dev Todo only seems to have 0% and 100% complete. Some gradation of completeness would be nice to add. As a hack for the time being, I tend to make up sub-tasks for each percentage of interest (say, 25%, 50%, and 75%), then mark them as done as I go along. However, it would be easier to do something like

tde -P 80 3

to mark task 3 as 80% done. One could also use the child percentages for calculation of parent percentages in terms of "done-ness".