File tree in file browser
This issue is based on the discussion in the following issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/13723#note_13717702 .
The following mockups have the updated looks of taken into mind from: https://gitlab.com/gitlab-org/gitlab-ce/issues/19616#note_13554002
The idea is an expansion on the existing repository file view, where you can simply expand the filetree view to look inside sub folders.
Single Source Of Truth
