spaces 6.x-2.0-beta6

This release contains one small but important API change: the $space->links() method has been split into $space->user_links() and $space->admin_links() to better differentiate and permission links pertinent to users of a space and those who pass the $space->admin_access() check.

Other changes

- Quoting array string key correctly in features preset export.
- Falling back to a default preset if the saved space preset is no longer valid.
- Adding drupal_alter() for spaces presets.