when a value is composed only with space tabs etc consider it as None

- Written a new custom_list validator, it takes another validator name as argument (in order to validate items of list)
- Using it to validate list of plugins names

Now when running distclean ALL files generated by the ./bootstrap && ./configure && make are deleted.
Maybe it's not a good idea because it's not the purpose of distclean target...

Using $pkgpythondir instead of $pythondir in Makefile.am
Solves a bug that put installed files in site-packages instead of dist-packages on debian

IMPORTANT : tests are broken. See details below

A new lodel/buildconf.py.ini file created. It will be transformed to a lodel/buildconf.py file by ./configure .
This file goal is to store build time constant (for the moment the presence of pymongo).
You have to build lodel2 before being able to run the tests.

- The validator is written and added to all Plugin sublcasses confspec
- Adds the capabilities to give args to validator (here we give the expected type)

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__

Import bugfixes in settings validator. Hooks must be imported in validatore definition to avoid circular import failure

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.

http://redmine.labocleo.org/issues/121

Check that an EmClass.EmField exsists in dyncode

- Replaced a self. by cls. in leobject
- Changed default value for runtest option

- now datasources are declared with two conf keys : read_only and identifier
- the old datasources plugin hook is now declared in lodel/plugin/core_hooks.py. This file is imported after lodel/plugin/hooks.py in the loader.py

- renamed Plugins class to Plugin
- an instance represent a loaded plugin
- classmethod allows to preload & load plugins

+ a new validator named 'string', it tries to cast the conf value using str()

To start in standalone uwsgi set lodel2.webui.standalone=True in conf file and start loader.py

- fixes exceptions output
- add "none" validator that validates only None