SortByDirection: due to relatively slow performance of AddRange library method, check if sorting changed the sort order of the articles and only clear and readd articles to list box if changed

Performance of check for change is 2 ms per 50k articles, AddRange just under 400 ms for same list

git-svn-id: svn://svn.code.sf.net/p/autowikibrowser/code@10348 5227b50d-9349-4574-b055-4b0a7525e11c
Fix previous

git-svn-id: svn://svn.code.sf.net/p/autowikibrowser/code@10349 5227b50d-9349-4574-b055-4b0a7525e11c
Update code comment

git-svn-id: svn://svn.code.sf.net/p/autowikibrowser/code@10350 5227b50d-9349-4574-b055-4b0a7525e11c
RemoveDuplicatesNew: avoid performance penalty of AddRange if deduplication didn't remove any articles

git-svn-id: svn://svn.code.sf.net/p/autowikibrowser/code@10351 5227b50d-9349-4574-b055-4b0a7525e11c
RemoveDuplicatesOld: performance improvement by using AddRange (1 second saved per 10k articles)

git-svn-id: svn://svn.code.sf.net/p/autowikibrowser/code@10352 5227b50d-9349-4574-b055-4b0a7525e11c
RemoveDuplicatesOld: avoid performance penalty of AddRange if deduplication didn't remove any articles

git-svn-id: svn://svn.code.sf.net/p/autowikibrowser/code@10353 5227b50d-9349-4574-b055-4b0a7525e11c
Filter namespace: avoid performance penalty of AddRange if filter didn't remove any articles

git-svn-id: svn://svn.code.sf.net/p/autowikibrowser/code@10354 5227b50d-9349-4574-b055-4b0a7525e11c