Now create the full FS structure associated with a multisite instance

Changing lodel2 to lodel again. Lodel2 was breaking the lodel package naming
it lodel2 leading to import failures when attempting to import lodel

The plugin and the settings classes are not able to use the logger in
early bootstrap stages. In order to see messages at thoses stages
we replace the logger by warnings.warn()

But a large majority of works remain !

Adaptation to the new datahandlers

Now we set a PYTHONPATH variable instead of hacking inside python code

Recent changes broke the 'deb' target building process. Now fixed and
back at work !

Better access to a few variables into the .am files. Allows for single
point of definition of variables required accross various .am.
For concerns separation, may probably switch from Makefile-common.am.inc
to Makefile-multisite.am.inc.

names was set to "sites_datas" isntead of "sites_data"...

Allows creating multisite instances, along with its directories creation
into /var/lodel2

Now an empty string is replaced by None

In order to have settings_loader #308 bugfix

Conflicts:
	lodel/editorial_model/model.py
	lodel/leapi/datahandlers/base_classes.py
	lodel/plugins/multisite/confspecs.py

It's only the begining, I have to make a commit in order to be able
to fix the settings on master