Override DownloadStore.prototype.load() to correctly load large data
See https://github.com/Infocatcher/Download_Panel_Tweaker/issues/5#issuecomment-35358879
(#5)
Extract dontRemoveFinishedDownloadsLegacy()
(#5)
Refactor patch for DownloadsDataItem.prototype.updateFromDownload()
(#5)