use it for all get operations

+ correctionde  bug dans users.ts

added 2 new fields in events : m_authors and m_recipients and miplmeneted both functions authors and recipients

Implementation des getAllMessages et compagnie

created and implemented simpleGroupsOfGroups in tool.ts to facilitate the implementation of other functions

Added 2 new function getAllQuestionsReceived and getAllAnswersReceived in messageModels that are not implemented yet