change vcs submit editor layout

make it two column layout
left column: VCS widgets and Description
right column: Files

Change-Id: Id9fb7e30d214d2bfad013d385ecfb7c9698fc046
Reviewed-by: Tasuku Suzuki <stasuku@gmail.com>
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>
Reviewed-by: André Hartmann <aha_1980@gmx.de>