Piccolo-admin

------
Added new UI for the foreign key selector.

-------------------------------------------------------------------------------

------
Fixed a bug where resetting the filters in the sidebar would set them to
``less than``. Now they reset to ``equals``. Courtesy sinisaos.

-------------------------------------------------------------------------------

------
Fixed a bug where a filter for a column with choices would default to
``'Null'`` instead of ``'All'``.

-------------------------------------------------------------------------------

------
Added a ``visible_filters`` option to ``TableConfig``, allowing the user to
specify which filters are shown in the filter sidebar. This is useful if you
have a lot of columns. Courtesy sinisaos.

Improved the navigation sidebar UI - each section can now be hidden, and the
appearance has been improved when table names are very long. Courtesy
sinisaos.

Added docs for Javascript formatting to help new contributors.

-------------------------------------------------------------------------------

------
Added ``TableConfig``, which allows more fine grained control over how the
UI behaves for a given ``Table``. Currently it allows you to specify which
columns are visible on the list page, but more options will be added in the
future. Courtesy sinisaos.

-------------------------------------------------------------------------------

------
Fixed bugs with nullable ``ForeignKey`` and ``Timestamp`` columns - the UI
would try sending back an empty string, instead of a ``null`` value. Courtesy
sinisaos.

-------------------------------------------------------------------------------