Django-sitecats

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* Fixed TypeError exception when get_category_lists() is used.

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+ Implemented `toolbox.get_category_lists()`.
* DB hits number decreased.
* Fixed number of ties calculation for items.
* Slight API changes.

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+ Implemented `category_separator` param support for category editor.
+ Implemented locked category restrictions for Django Admin.
+ Implemented category choices for editors.
+ Implemented `sitecats_url` template tag.
+ get_category_aliases_under() added into toolbox.
+ CategoryRequestHandler error messages now can be customized.
* Fixed category ordering.
* Fixed rendering category with no subcategories in editor.
* Fixed Cache._get_cache_entry() fail to get categories from root.

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+ Basic functionality.