Revert "refactor mongo cursor"

This reverts commit 0cd8fd20f4b2a74ad956c1096f7386b9f871dbe2.

Conflicts:
	src/Norm/Connection/MongoConnection.php
	src/Norm/Connection/OCIConnection.php
	src/Norm/Cursor.php
	src/Norm/Cursor/MongoCursor.php
	src/Norm/Cursor/OCICursor.php