closes #53
move dislike query
rename user_like_group table to user_dislike_group  -> closes #66
bugfixes in messagemodel

 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