actionBinding: Remove check for QControlBinding when unbinding.

If it's the associated object, it's the target, and it's being unbound,
it needs to be removed regardless of whether it's a QControlBinding.
document: Implement usesUbiquitousStorage.

Returns false, not that there's any way to use iCloud out of the box
anyway.
Remove extraneous newlines.
rule: Remove needless casts when working with plists/strings.

- settings will be implicitly converted to a QPropertyList as needed.
- scope is already a string.