[daip] IMAGR, clean, spectral line data

[Gustaaf van Moorsel]

As far as I know, IMAGR, when mapping and cleaning a spectral line
data set, does not allow specification of a separate box for each
channel.  I think it would be a good idea to think about adding
this as an option (though I realize this may be a major effort).

For instance, a separate verb or task could step through a cube
and record the boxes for each channel, which are then used as in-
put to IMAGR.  Even if only one box per channel were allowed, this
would make life for many spectral line observers much easier.

Apologies if this option already exists, in which case I missed it.

Thanks,

Gustaaf