Hopefully this will make it much easier to deal with later, and hopefully this
will help to flush out the remaining duration-calculation-related bugs by
avoiding repetition of the calculations. Various minor fixes in the process.
I'm not convinced this is completely bug-free yet, of course, but it does
seem at least to be slightly less broken than before, so.
existing timed tasks and milestones in that they have a duration that
increases based on the amount of time tracked for them, and no set
completion time. Nearby minor fixes.
column to PM_task. Also move the bulk of the PM project display JS
stuff into a separate JavaScript file rather than it being in a template
in the database.
