Looks better and matches the Gtk client.
Co-authored-by: dubhater <cantabile.desu@gmail.com>
Co-authored-by: Mike Gelfand <mikedld@users.noreply.github.com>
Split FileTree.{h,cc} and FilterBar.{h,cc} files so that each class
is in its own file.
This breaks translations (some classes got renamed => context changed),
to be fixed by next commit (along with Tx sync).