user is a contact
NewUser can have a main_user_id
filter correctly on base core
raise if user_name already exist
authenticate by name not user_id
raise if contact to delete is user one
move class to format a mail message to a parameter into a dedicated package
s/user_name/name
check for reserved user names configuration definition
move user message delivery logic into user package
Merge pull request #4 from gdchamal/parameters

Core object use of schematics parameters
fix import du to previous move
no more dependency amongst pyramid in core package
add core exceptions, NotFound as first one
remove by_id methods, need fix output format
NotFound exception defined in storage package
includeme can be called with a parameter from a pyramid app
do not ouput ourself as contact
Thread.get natural way, need a method for index lookup with expands
fix message.from_ value in most case, need better validation