Now the _LeObject.get() method should be able to return LeType child classes instance
LeType has two new methods :
	- LeTypes.datas() @property method that returns a dict(FIELDNAME:FIELDVALUE)
	- LeType.populate() that fetch from datassource missing fieldvalues

An old string was given as argument to DummyMigrationHandler and was interpreted as debug = True

Added a test on LeFactory generated code

Associated tests has been added/updated

Update the associated tests

Methods are _LeObject.get() and LeType.check_datas()

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

Checking that internal='object' is reserved for common fields

This method split a string in a tuple(FIELD, OPERATOR, VALUE)

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