ZODB Components: Likewise Document, add Mixin (erp5.component.mixin) and Interface (erp5.component.interface).

* One Mixin/Interface class per ZODB Component.
  => Already the case for FS Mixin, not for Interfaces.
* ZODB Components module name ('reference' property) and class name:
  + Mixin: FooMixin.
  + Interface: IFoo.

Rationale:
  + Avoid current FS hacks: registry (Mixins, mixin_class_registry) or import
    all classes explicitly in __init__.py (Products.ERP5Type.interfaces).
  + Consistent naming.
  + Consistent with ZODB Documents Components.

Also, modify pylint checker to handle Zope Interfaces:
  + E: 4, 0: Inheriting 'Interface', which is not a class. (inherit-non-class)
  + E: 5, 2: Method has no argument (no-method-argument)