There's no point having both movement_direction and wlr_direction. This
replaces the former with the latter.
As movement_direction also contained MOVE_PARENT and MOVE_CHILD items,
these are now checked specifically in the focus command and handled in
separate functions, just like the other focus variants.
When we have type safety we'll need to have functions for
workspace_add_tiling and so on. This means the existing container
functions will be just for containers, so they are being moved to
container.c. At this point layout.c doesn't contain much else, so I've
relocated everything and removed the file.
* container_swap and its static functions have been moved to the swap
command and made static.
* container_recursive_resize has been moved to the resize command and
made static.
* The following have been moved to container.c:
* container_handle_fullscreen_reparent
* container_insert_child
* container_add_sibling
* container_add_child
* container_remove_child
* container_replace_child
* container_split
* enum movement_direction and sway_dir_to_wlr have been moved to util.c.
Side note: Several commands included layout.h which then included
root.h. With layout.h gone, root.h has to be included by those commands.
