[Kst] Plugin output naming

[James Churchill]

I currently have a data source with six input vectors, and I want to
run the Statistics plugin on each one. Unfortunately, doing so gives
me multiple data objects all called "Statistics Plugin Object", and no
easy way to identify which is which, except for manually recording the
P and X numbers for the scalars I want in the data manager before
trying to use them in expressions. Even worse, it's not possible to
rename these objects, as Kst insists on reverting to the default name.

I see a similar bug exists and was fixed for Kst 1.x, and it looks
like a similar omission has occurred for 2.x. Too bad the codebases
are so different!

- James