Updated to store/retrieve "activity <=> desktop id" only to/from KConfigGroup.
Seems to work just fine :-)

Patches kactivitymanagerd to store (and restore back) the working current directory when switching activities.

The activity-changing-behavior is as follows:
1.  Say you have two (or more activities) A and B.
2.  You are working on activity A on Desktop 4.
3.  You switch to activity B (and by default to Desktop 4).
4.  Change to Desktop 1.
5.  Go back to activity A and (by default) to Desktop 1, while it should move you to Desktop 4 (this is where my patch kicks in).

I hope it makes sense :-)