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/fulltext.cpp

@@ -275,7 +275,7 @@ FullTextResult FullText::find(const FullTextQuery &q, StringFilterMode mode) con
 				[&res2] (dive *d) { return std::find(res2.begin(), res2.end(), d) == res2.end(); }), res.end());
 	}
 
-	return { res };
+	return { std::move(res) };
 }
 
 FullTextQuery &FullTextQuery::operator=(const QString &s)