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

Problem description
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This is the second part of ticket #1002 

It tried to clean the exception handling in chevah.utils package.


Changes description
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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
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Nothing special here.