[#1120] Remove prefix and section_name for the interface declaration.

Problem description
===================

The IConfigurationSection is defined as a storage independent object.

_prefix and _section_name are options required only by File storage persistance.

_proxy is the generic object used to access the persistence.


Changes description
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attributes were removed.


How to try and test the changes
===============================

reviewers @alibotean 

This should be simple.