refs #132

Now backref seems to work at creation of a Person linked with a text the Person UID is appended to Text.linked_persons

Triggered a bug in wrong Integer DH tests

Methods are written.
They are not called by anyone and the only tests that were done is that no syntax error is raised.
( refs #131 )

Created groups (they can be found under the "Modules" menu -_- )
Created new pages : on LeAPI EditorialModel Plugins etc

- webui fix in cookies handling
- ram_session fix in token generation (return an str : hex representation of os.urandom(n))
- more fixes in Client session handling

No need of -d flag to specifiy directories

Created a new class LodelSession to handle session datas
Created an automatic wrapper to acces to session handler plugin function throug SessionHandlerPlugin class methods
Bugfixes done for plugins. The plugin type is store in __plugin_type___ and not in __type__

Implements both Plugin child classes handling extensions and session handling.
Modified the settings plugin preload piece of code. It is now adapted to the new plugins organisation.
Each Plugin child classes provides a confspec indicating where the plugin list is stored in configuration.

- now plugin is able to instanciate using the good child class
- the discover cache now contains plugin's type