erp5_core: fields of default field library must not be mandatory

By default in ERP5 all fields are not mandatory

product/ERP5/bootstrap/erp5_core/SkinTemplateItem/portal_skins/erp5_core/Base_viewFieldLibrary/my_multi_check_box_field.xml

@@ -217,7 +217,7 @@
                 </item>
                 <item>
                     <key> <string>required</string> </key>
-                    <value> <int>1</int> </value>
+                    <value> <int>0</int> </value>
                 </item>
                 <item>
                     <key> <string>title</string> </key>
@@ -231,8 +231,7 @@
                     <key> <string>view_separator</string> </key>
                     <value> <string encoding="cdata"><![CDATA[
 
-<br />\n
-
+<br />
 
 ]]></string> </value>
                 </item>