[Kst] branches/work/kst/portto4/kst

[Brisset, Nicolas]

> Add Save/Restore for DataSources.
A rather tricky point from my past experience, especially when/how/where
to store file-speficic configuration as could be entered in the data
wizard by clicking "Configure...", for the datasources that provide
config options of course ! I don't know whether things have come that
far in kst2 yet, though. I'd really need to take some time to look at
the new datasource specs, but right now I'm completely overwhelmed in
urgent things that have nothing to do with kst :-(

> Modify loading of DataSources 
Another thing that led to discussions in the past, particularly for
performance reasons. It is good to cache datasources, and call the
contructors only once because in some cases the complete file is parsed
and that can take quite a lot of time. Getting the list of variables
should be fast, e.g. to avoid freezing the data wizard in the first
steps. Another option would be to slightly change the datasource API and
add an init() stub that can be called only when needed and that would
contain the more expensive init stuff.

Nicolas