In multisite loader utils

In this state I was able to insert a new site. But only the mongodb datasource
seems to have receive the query (inserted in DB but not created on FS).

Conflicts:
	lodel/editorial_model/components.py
	lodel/editorial_model/model.py
	lodel/plugin/plugins.py
	lodel/plugins/Makefile.am
	lodel/plugins/webui/templates/admin/editable_component.html
	lodel/validator/validator.py
Revert:
	lodel/validator/validator.py 3d51695ea6
		The hook HAS TO be registered even if not value !

Deleted hardcoded Object class name + adding support for varchar & text
in editable_component template

Now it seems to work. Tested using :
dummy datasource, no handled sites, ipython ui

Conditionnal plugins path given the context type (mono or multi site)

Now the directory tree looks like :
.sites_context/lodelsites/NAME/__init__.py
.sites_context/lodelsites/NAME/leapi_dyncode.py
.sites_context/lodelsites/NAME/lodel/ <- symlink

Only tested for lodelsites instance

The is_instance test on classes loaded from a pickle file is not
relevant :
lodel.editorial_model.components.EmClass != lodelsites.__loader__.editorial_model.components.EmClass

There is a problem left : when dyncode runs an error is triggered telling
that no active clases were found

Now both __loader__ and lodelsites contexts are using the same configuration
files and the same confspecs.

Now using mass_deploy and slim seems to work for a monosite

Now create the full FS structure associated with a multisite instance