[Kst] Plugin documentation update

[Brisset, Nicolas]

I am just not sure: should I 
1) file bug report(s) regarding the plugin _doc_ being out of date ? 
2) try to guess how things should work from the examples in the kst
distribution and be quiet about it so that there don't appear zillions
of plugins based on subtleties of the current system, leading to a lot
of porting effort when we change the plugin system later ?
3) commit updates to the appropriate file in devel-docs as I get along
so that we have clear ideas of what is being used ?
4) [other] 

Nicolas