VisAD SpreadSheet now supports multiple data per cell

It is now possible to load multiple data objects into a
single spreadsheet cell, overlaying them in one display.
I am in the process of updating the SpreadSheet web site
(http://www.ssec.wisc.edu/~curtis/ss.html) now.

In addition, I have overhauled much of the SpreadSheet's
code, including the collaboration support from the
ground up.  The visad.ss API has changed noticeably in
support of multiple data per cell, and quite a few
methods have been deprecated.  If you have an
application built on top the visad.ss API, it should
still work, but it will report using a deprecated API.

I have undoubtably introduced some bugs in this version,
but many bugs have also been fixed.  If you find a bug,
especially something that worked in the old SpreadSheet
but now no longer does, please report it to
curtis@xxxxxxxxxxxxx and hibbard@xxxxxxxxxxxxxxxxxx

Thanks, and I hope everyone enjoys the new SpreadSheet!

Curtis