Compatibility with sf2.4

The class FormException is now an interface. https://github.com/symfony/symfony/blob/d221a697c781d0a92a74e7054b7c991ffcdeed70/UPGRADE-2.2.md#form
Update AjaxAutocompleteType.php
Update AjaxAutocompleteType.php
Update AjaxAutocompleteType.php
Update DependentFilteredEntityType.php
Update DateRangeType.php
Update AjaxAutocompleteType.php
Update DependentFilteredEntityType.php
Update DateRangeType.php
Update AjaxAutocompleteType.php
Merge pull request #60 from Troytft/patch-1

Compatibility with sf2.4