Add master = true to uwsgi.ini

Add the custom message provided by HttpException to the template

Before when session restore fails the webui was answering "Unknown status 200" as content.
Now it produce 2 log messages (maybe)

broken nginx conf + absolute path in slim that is known only at build time

using --plugin option instead of uwsgi_python3 shortcut (can be uwsgi_python34 etc)

Adds a LODEL2LOGDIR to buildconf.py
Adds a nginx-conf option to slim
...

Now create an INSTANCE_NAME.sock in @localstatedir@/uwsgi_sockets
Note : the localstatedir is wrong -_- /usr/var instead of /var........

Using execl instead of fork to preserv the pid

SLIM is now able to edit configuration from CLI, to start instances 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

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__