The default setting for unassigned keybindings is now correctly
represented by an empty list as opposed to a list with an empty
keybinding ("").

Replaces the `resize-up`, `resize-right`, `resize-down` and
`resize-left` setting entries with the following, more exhaustive
settings:

- `contract-left`
- `contract-right` (replaces `resize-left`)
- `contract-up`
- `contract-down` (replaces `resize-up`)
- `expand-left`
- `expand-right` (replaces `resize-right`)
- `expand-up`
- `expand-down` (replaces `resize-down`)

BREAKING CHANGE
Users with custom keybindings for any of the replaced settings will
have to manually rebind those in accordance with the new setting keys!

The autotile feature had previously calculated the window layout by
considering both minimized and unminized windows. This led to empty
areas when using the autotile feature on a screen with minimized
windows.