ZF-6925: decline Zend_Pdf_PhpArray usage


Zend_Pdf_PhpArray class was designed to give an ability to track PDF array elements updates and to unify access to PDF elements (to eliminate differences between objects and other php types - sending as parameter and assignment "by reference" or "by value"). Automatic PDF elements value updates were declined later because of performance considerations and actual items PDF array collection was aggregated by Zend_Pdf_Element_Array class. This gives an ability to decline Zend_Pdf_PhpArray usage and this may give some PDF processing performance improvement.