TQSampleFolder generalizeObjects wastes performance

The downmerging feature of SampleFolders is currently missing out on disabling the style application on the TQSampleDataReader instances it uses internally. For downmerging, however, we should not be bothered about applying styles to the objects being merged. A quick test with a dozen input files for tqmerge (in all cases the objects are already very close to or even at the destination, so the effect here should be small) shows a speedup from 1:23 (m:s) to 0:54 on a local laptop...