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__

Updated interface with nex dyncode

- Implemeting Client in plugins/webui/client.py
- Calling client in run.py

- webui now calls a hook to indicate a session end
- loader.py now set a lodel.dyncode module exposing dynmically generated code

- creating a function in webui/main.py root_url() that returns the root url without trailing /
- use this function in router and template/loader