Suppression du init et passage des classes plutôt que les instances pour les fieldtypes dans le _fields

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

Cleaning code for EmComponent
Optimizing tests for EmComponent and EmFieldGroup (running initDb in setUpModule and make a backup copy, the backup is restored in setUp)

- Now except for the modify_rank tests test_component didn't fails
- Added simple integer operation capabilities to EmFieldType_integer ( int cast, +=, -=, *=, /=, +, -, *, /, %, ...)

Maybe very bugy

Written some test setup and the begining of the __init__ test

- Added a _fields property (also added it as class property, but the way its done is not satisfactory... we want an ordered dict and not a tuple list as class property)
- Its now allowed to give an uid or a name as em_class for EmFieldGroup.create(name, em_class).
- Now when EmFieldGroup.create is called with an existing name it raises an error (ValueError)
- Removed EmFieldGroup.populate and EmFieldGroup.save

Using sqlite db in test_components

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

Correction du bloc de mcommentaire de class encore sous l'ancien modèle.

remplacement des self.id restant par self.uid

Changed id in uid and changed the dummy class for testing

Now EmComponent is populate if it's instanciated with a name or an id

runtest script has now comments inside showing usefull options to run tests

Added tests for newUid, __init__, save and modify_rank

Written test environment init
Written test for newUid and __init__