ZF-11511: no support to extra plugins like ordinary plugins


the class Zend_Dojo_Form_Element_Editor has ordinary plugins operations but doesn't allow us to use similar methods for extra ones.

extra plugins are part of {{dijit.editor}} component as can be seen here:…

suggested additions to class {{Zend_Dojo_Form_Element_Editor}} and suggested test units for being add to class {{Zend_Dojo_Form_Element_EditorTest}} can be found attached.

the fix for this depends on ZF-5711


Patches applied to trunk. As this provides new features, I have not merged into the 1.11 release branch. If we do a 1.12 release branch, the features will be incorporated; I will also clone the issue to the ZF2 project so that the support will be pushed upstream.