Cette vérification est prise en charge dans EmComponent

Behaviour changed for EmComponent and childs create method :
	- Takes care of duplicated names at creation
	- Handle all the checks in EmComponent method
Factorization of EmField.get_class_table() method
Added a @property method class_table_name to EmClass

Every tests passes, except the skipped tests on relation_to_type links
There is a strange warning that comes maby from some tests (but maybe not)...

The EmField version cannot be tested yet (drop column not yet implemented for sqlite in Database.sqlalter)

ignoring:
 - line too long
 - doctring

Now _fields and table MUST be class attribute.
Its important to note that _fields now consist in a list of (name, ftype) tuples and that ftype is a EmFieldType class and NOT an EmFieldType instance

EmComponent.create() now takes keywords arguments corresponding to the _fields property of the calling class

WARNING !!! Hardcoded rank = -1 at component creation and Hardcoded 0 as default value for EmClass icon

The dates are set in EmComponent::create() for date_create and in EmComponent::save() for date_update
The values are sets to datetime.datetime.utcnow() so we now that EVERY date in the db are in UTC, no matter django, database or even server configurations.
We will have to take care to convert dates from database to django timezone in dates fieldtypes.

Added a classmethod EmComponent::newUid() that determines the caller's class and return a newly registrated UID

SQL calls are in _populateDb , _saveDb and _createDb methods (exception for component::delete() )

Lodel/sttings/__init__.py wasn't able to import files when called by manage.py
Renaming em to EditorialModel and moved Em* objects to EditorialModel/lib
Adding a first test (that do not pass because of syntax errors in Em* classes)