Portlets can work on Plone4 and on Plone5

Fixes:
```
2014-11-26 15:52:56 ERROR Zope.SiteErrorLog 1417013576.860.439679399488 http://localhost:8080/Plone/++contextportlets++plone.rightcolumn/+/plonesocial.microblog.portlet
Traceback (innermost last):
Module ZPublisher.Publish, line 138, in publish
Module ZPublisher.mapply, line 77, in mapply
Module ZPublisher.Publish, line 48, in call_object
Module plone.app.portlets.browser.formhelper, line 59, in __call__
Module z3c.form.form, line 218, in __call__
Module plone.z3cform.fieldsets.extensible, line 58, in update
Module plone.autoform.form, line 33, in updateFields
Module plone.autoform.base, line 54, in updateFieldsFromSchemata
Module plone.autoform.form, line 22, in schema
NotImplementedError: The class deriving from AutoExtensibleForm must have a 'schema' property
```