[daip] IMAGR destroys previous image

[Craig Walker]

I've just had a situation where, after various tgets etc, I mistakenly
ran an IMAGR with the outname and sequence of a previous imaging
effort.  The source is different, the input uv data set is different,
and the observing day is different.  But IMAGR wrote over my previous
image, destroying the old one in the process.  I can see why IMAGR
will write over an old version for restarts etc.  But PLEASE build in
some protections against what should obviously have been a mistake
in my part.  Now I have lost the final results of my previous imaging
effort.  Fortunately, it won't be too hard to recover, but it is still
a pain.  Even an "are you sure" message, as from EXTD when deleting CL 1,
would be useful.  But the major differences mentioned earlier should
have been a strong indication that this was an error.

Craig