[GTKUI] Add new OtherDialog to dialogs

This adds a new OtherDialog to dialogs so that will use Deferred to prevent
the dialog loop locking up the mainwindow.
Remove old `Other` dialog from common and cleanup up the file.
Fixes #2401, context menus for torrents not showing current value.
Fixes #2400, add a stop_at_ratio context menu.
Change the protocol rate to display as int.