[Kst] Change data file problems...

[Brisset, Nicolas]

It seems we have problems with the change data file tool. Sometimes, the
data is not properly updated, and after a while the data manager shows
even more chaotic info than the curves themselves. It looks like some
updates are not propagated correctly, and things tend to get out of
sync. 
We are working on isolating a test case, if I have one I'll open a bug
but for now I can only mention that there are problems. No idea whether
reading the code alone might help, though...

Nicolas