Releases for Hierarchical Select

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!

Bug fixes
- Fixed: the select items of the current HS aren't disabled when it's waiting for a server response.
- #212528: Weight of vocabulary has disappeared from the form
- #212052: When dropbox limit is reached: display warning, disable hierarchical select

New features
- Feature: support for subscriptions_taxonomy module.

Improvements:
- #205123: Better default theme
- Only prepend a "none" option to the root level if the form item is optional AND (this is new) if the "enforce deepest" option is enabled.
- Documented special values.

Bug fixes:
- #205341: Selection lost on preview
- #206598: Incompatible with Content Taxonomy.
- Dropbox title not being passed through, thus is reverting to default title after a dropbox entry was added/removed.

New features
- Implemented #176936: support for multiple select. Sponsored by Paul Ektov.

New features:
- Added the ability to have an optional hierarchical_select form item, and immediately added support for this in the taxonomy hierarchical select rendering function. (#173052)

Bug fixes:
- Fixed CSS bug that caused misalignment of selects when JavaScript was disabled.
- Fixed #181701: Hierarchical Select fails to update when the server doesn't support clean urls
- Fixed #178748: On submit if the form has validation errors then the select box selects the default category.

Initial release.