TKTService: extract serviceManager slot?

[tinchodias]

There is TKTConfiguration serviceManager in the methods kill, start and stop, and an additional occurrence in TKTWatchDog.

I guess we can introduce a serviceManagerslot which brings the feature of allowing setting a different service manager than the global.

[tinchodias]

I looked at the references to TKTConfiguration from several classes in Taskit (41 occurrences in the default group that I loaded, such as TKTWorker, TKTFuture, TKTTask). I think that it may be a better idea to create a 'configuration' slot to replace the global reference in those classes. Does it make sense?