Add possibility to hide empty value in customfield group view rendering

A new parameter is defined :

```
chill_custom_fields:
    show_empty_values_in_views = true|false
```

A new method is added to CustomFieldInterface: `isEmptyValue`. To ease
the dev of new classes, an AbstractCustomField class is created, which
implements the most commons function (currently, only isEmptyValue).

A new Twig Filter is added: `chill_custom_field_is_empty`

The twig filter `chill_custom_fields_group_widget` has a new possibility
in array option : `show_empty`. Default to
chill_custom_fields.show_empty_values_in_view. May be forced by
true/false.

CustomFields/AbstractCustomField.php

@@ -0,0 +1,37 @@
+<?php
+
+/*
+ * Copyright (C) 2015 Julien Fastré <julien.fastre@champs-libres.coop>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Chill\CustomFieldsBundle\CustomFields;
+
+use Chill\CustomFieldsBundle\CustomFields\CustomFieldInterface;
+use Chill\CustomFieldsBundle\Entity\CustomField;
+
+/**
+ * 
+ *
+ * @author Julien Fastré <julien.fastre@champs-libres.coop>
+ */
+abstract class AbstractCustomField implements CustomFieldInterface
+{
+    public function isEmptyValue($value, CustomField $customField)
+    {
+        return (empty($value) and $value !== FALSE);
+    }
+    
+}

CustomFields/CustomFieldChoice.php

@@ -38,7 +38,7 @@ use Symfony\Component\Translation\Translator;
  * @author Julien Fastré <julien.fastre@champs-libres.coop>
  * @author Marc Ducobu <marc@champs-libes.coop>
  */
-class CustomFieldChoice implements CustomFieldInterface
+class CustomFieldChoice extends AbstractCustomField
 {
     const ALLOW_OTHER = 'other';
     const OTHER_VALUE_LABEL = 'otherValueLabel';
@@ -174,6 +174,11 @@ class CustomFieldChoice implements CustomFieldInterface
     {
         return 'Choices';
     }
+    
+    public function isEmptyValue($value, CustomField $customField)
+    {
+        return $value['_choices'] === NULL;
+    }
 
     /**
      * 

CustomFields/CustomFieldInterface.php

@@ -58,4 +58,12 @@ interface CustomFieldInterface
      * @return \Symfony\Component\Form\FormTypeInterface|null the form type
      */
     public function buildOptionsForm(FormBuilderInterface $builder);
+    
+    /**
+     * Return if the value can be considered as empty
+     * 
+     * @param mixed $value the value passed throug the deserialize function
+     * @param CustomField $customField
+     */
+    public function isEmptyValue($value, CustomField $customField);
 }

CustomFields/CustomFieldLongChoice.php

@@ -33,7 +33,7 @@ use Symfony\Bridge\Twig\TwigEngine;
  *
  * @author Julien Fastré <julien.fastre@champs-libres.coop>
  */
-class CustomFieldLongChoice implements CustomFieldInterface
+class CustomFieldLongChoice extends AbstractCustomField
 {
     /**
      *

CustomFields/CustomFieldNumber.php

@@ -39,7 +39,7 @@ use Chill\MainBundle\Templating\TranslatableStringHelper;
  * @author Julien Fastré <julien.fastre@champs-libres.coop>
  * @author Marc Ducobu <marc@champs-libres.coop>
  */
-class CustomFieldNumber implements CustomFieldInterface
+class CustomFieldNumber extends AbstractCustomField
 {
     /**
      * key for the minimal value of the field

CustomFields/CustomFieldText.php

@@ -33,7 +33,7 @@ use Chill\MainBundle\Templating\TranslatableStringHelper;
  * @author Julien Fastré <julien.fastre@champs-libres.coop>
  * @author Marc Ducobu <marc@champs-libres.coop>
  */
-class CustomFieldText implements CustomFieldInterface
+class CustomFieldText extends AbstractCustomField
 {
     
     private $requestStack;

CustomFields/CustomFieldTitle.php

@@ -28,7 +28,7 @@ use Symfony\Component\HttpFoundation\RequestStack;
 use Symfony\Bundle\TwigBundle\TwigEngine;
 use Chill\MainBundle\Templating\TranslatableStringHelper;
 
-class CustomFieldTitle implements CustomFieldInterface
+class CustomFieldTitle extends AbstractCustomField
 {
     const TYPE = 'type';
     const TYPE_TITLE = 'title';
@@ -92,6 +92,11 @@ class CustomFieldTitle implements CustomFieldInterface
     {
         return 'title';
     }
+    
+    public function isEmptyValue($value, CustomField $customField)
+    {
+        return false;
+    }
 
     public function buildOptionsForm(FormBuilderInterface $builder)
     {