Pass current session config to new window plugins

Review Request #110731 - Created May 30, 2013 and submitted - Latest diff uploaded

Kåre Särs
cullmann, dhaumann
With this patch, the KConfig of the current active session is passed to new main windows plugins. This is not done currently and thus the plugins of the new windows get the default session KConfig. 

This patch also changes the groupperfix passed to the plugins to not increment the mainwindow index. As writeSessionConfig() is only called for the last main window, we could get to situations where the last window is not the first main window and we would loose all the settings. 

There seems to be some session config mechanism that does not work as it was originally intended...

This patch is supposed to fix at least partially. The new window plugins would get the same config as the first main window and the last window to be closed writes its config to file.
Tested with gdb, search, ctags and build plugins.