hierarchical_select 5.x-2.0-rc4

I've been adding new features in almost every beta/RC. Not anymore now.

There's one known issue in this release. The reason it's not fixed yet: I've not yet been able to reproduce it.

New features:
- JS-enhanced Hierarchical Select settings form on the Vocabulary settings form
- New: Level label support when enforce_deepest is enabled; level labels will only be allowed in the root level.
- Smarter default settings for #required and #multiple for the exposed filter overriding.
- New: ability to set a root level label when enforce_deepest is enabled.

Improvements:
- Improvement: more consistent use of the "" option, available when: optional, or enforce_deepest is enabled, or multiple select is active and at least one item is selected.
- Improvement: the "" option is now automatically selected as soon as at least one item has been added to the dropbox (even if it's a required form item) – this required changes in the client-server interaction.
- Improvement: more reliable lineage reconstruction algorithm when save_lineage is enabled.
- Improvement: all_option setting now only has effect when multiple select is enabled (minor).
- Improved: Made selection of value 'label_X' trigger similar events as 'all' value: no server query required!
- Improved: animation for the non-server-query options is now different from the "normal" one.
- Improved: Made selection of value 'none' trigger similar events as 'all' value: no server query required!
- Improved: made all cases in the updateOriginalSelect() method use the same $options jQuery element set.
- Improved: level labels UI.
- Added entry to README for #207252: content_taxonomy PHP errors when set to save in CCK table.
- Add documentation for all_option setting.

Bug fixes:
- Fixed #217538: Unselecting 1st level terms using "none" doesn't remove second-level dropbox