Update FOF to 2.1.rc4

This only updates FOF to 2.1.rc4, including bug fixes affecting display issues under Joomla! 3.2.

Joomla! issue tracker [#32381](http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=32381)

Summary of changes:

    + Added DTD for XML forms under documentation/form.dtd
    + Add Joomla formatter for FOFLess
    + 'btn' class assigned to buttons of fieldsearchable by default (adheres to Joomla! 3 styling guidelines)
    + Using icons for fieldsearchable's search/reset buttons
    ~ Update to lessc 0.3.9
    ~ FOF table caching now respects Joomla! caching options (is it enabled, cache handler and cache lifetime).
    # Error when deleting entry of FOFTable which is using assets
    # jquery.ui.tooltip.js in AkeebaStrapper::jQueryUI() breaks Joomla 3 tooltip
    # JHtml::_('behavior.multiselect') must be loaded in Joomla 2.5 and for FOFRenderJoomla
    # Unable to add component-specific behaviours to models
    # Fix loadTemplate behaviour on J3+
    # When the table cache reports a table as non-existent (e.g. the server failed to reply to SHOW TABLES) you had to clean the cache to see the table in FOF
    # JFormField changes in Joomla! 3.2 Beta 1 broke FOF form fields