Filewatch: move all filewatching into the filewatch service

Remove watch adding in the fileindexer service.
On a config change they were previously being re-added twice.

Then watch all indexed folders in filewatch constructor.
This is needed so that nepomukctl restart filewatch watches all indexed folders.
Don't bother to wait two minutes before installing the watches - it
isn't that slow anymore and we were doing most of the work anyway by
watching the homedir on startup.

REVIEW: 110301