Checks for EmField :
- checks that the name is uniq in an EmClass
- checks that a relation EmClass <- rel2type -> EmType is uniq

Associated tests has been added/updated

Now on load default fields for EmClass are created. The EmClass.check method create them if they are not present.

Added default fields for EmClass, they are listed by classtype in EmClassType
Fixing some tests (testing that a new EmClass has no fieldgroups)
Fixing the delete_check of EmClass. Now an EmClass can be deleted if it contains only default fieldgroup and default fields

LeFactory.generatePython() is a method that generate LeObject code and python classes for each EmClass and EmType in an EditorialModel

Add a check for the default value
Removed the _fieldtype_instance attribute

No extended checks was done. Only tested if the check passes without syntax error and without failing with no reason

- Suppression du create / delete et des autres méthodes associées
- Suppression des imports qui sont devenus obsolètes

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