cleanup: more Coverity silencing

Mostly irrelevant std::move() stuff of copy-on-write Qt objects,
a few real bugs, a timestamp_t downconversion and some codingsyle
adaptation.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

core/videoframeextractor.cpp

@@ -112,7 +112,7 @@ void VideoFrameExtractor::processItem(QString originalFilename, QString filename
 		return fail(originalFilename, duration, true);
 	}
 
-	emit extracted(originalFilename, img, duration, position);
+	emit extracted(originalFilename, std::move(img), duration, position);
 	QMutexLocker l(&lock);
 	workingOn.remove(originalFilename);
 }