[daip] Feature request -- mean time of data selection

[Walter Brisken]

I'm not sure if this can be done easily or not, but it would be nice if
one could provide a data selection (ie, use standard adverbs including
flagging and data weights used in tasks like imagr) and return a weighted
mean time of the selected data.  One could imagine getting fancy and
having the user supply a robustness and a spectral index for additional
exactness of weighting, but even without these details such a task would
be useful.  Even better would be if this could be embedded in the image
keywords and for this information to be propagated through to JMFIT's
output.

-W