FilterNonMainArticles: improve performance when number of articles to be removed is < 1% of total

git-svn-id: svn://svn.code.sf.net/p/autowikibrowser/code@10355 5227b50d-9349-4574-b055-4b0a7525e11c
Find mode: for performance limit tree view to first 500 results

git-svn-id: svn://svn.code.sf.net/p/autowikibrowser/code@10356 5227b50d-9349-4574-b055-4b0a7525e11c
Text file loader: tweak regex to reduce backtracking

git-svn-id: svn://svn.code.sf.net/p/autowikibrowser/code@10357 5227b50d-9349-4574-b055-4b0a7525e11c
Fix RemoveSelected change from 10343 to use right option when first article is included in selection

git-svn-id: svn://svn.code.sf.net/p/autowikibrowser/code@10358 5227b50d-9349-4574-b055-4b0a7525e11c