[#1052] Remove usage of OperationlException. Use UtilsError.

Problem description
===================

reviewers @adiroiban

This is the second part of ticket #1002 

It tried to clean the exception handling in chevah.utils package.


Changes description
===================

I have remove all exceptions that are only used in the server.

chevah.utils package will now raise only ChevaUtils errors in public API.

All exceptions/error have no unicode ids.


How to try and test the changes
===============================

Nothing special here. I ran test_remote all and all looks ok.