time_begin/end params in ipp_detrend_combine.pl

[rodney]

With the essence data it is desirable to create one bad pixel mask for year 2003 and another separate one for 2004-2005 (the broken chip in 2003 was fixed for 2004+). I can set the time_begin and time_end parameters when running dettool to create a FLATMASK and DARKMASK. Then when I combine multiple masks together using ipp_detrend_combine.pl, a new detRun is created with det_type MASK, but it has NULL values for the time parameters.

It would be nice to have a command-line argument for -time_begin and -time_end.

It would be even nicer to have (in addition) some inheritance of the time parameters from the input masks.