remove getRecentLivePrefListWithClicklog()
remove _getRecentLivePrefListWithClicklog()
simplify _getRecentLivePrefList()
make _getRecentLivePrefList() inline
remove dependency on SearchDBHandler
remove SearchDBHandler
remove unused imports
remove non-existing create_torrent_signature()
remove ClicklogSearch table and index
Merge pull request #585 from LipuFei/fix-termfrequency

Remove SearchDBHandler and fix TermFrequency problem