Migrate of erp5_base-related source files to ZODB Components

@nexedi This is about migrating 65 files (Documents, Interfaces, Mixins, Unit Tests and Tools) from filesystem to ZODB Components. The reason I have created this MR is to discuss the following important points:

• Import statements will have to be changed in projects. For example: Products.ERP5.Document.Person will have to be changed to erp5.component.document.Person and modules doing such import at top-level will have to be migrated to ZODB Components too.

  This is necessary because import of Products modules and their registrations are done at a very early stage when starting Zope (even before erp5.component module is created). I currently don't see a way to do otherwise but any idea is welcome (I can provide a shell script to update imports so I don't think it's such a big problem though).

• Filesystem Interfaces are registered in Products.ERP5Type.interfaces. To have the same mechanism with ZODB Components, this would require loading all Interfaces at startup/reset which is obviously not a good idea. This means that the following common pattern:

  from Products.ERP5Type import interfaces class Foo: zope.interface.implements(interfaces.IFoo,) will have to be changed to (and for the same reason as above, this module will have to be migrated to ZODB Component):

  from erp5.component.interface.IFoo import IFoo class Foo: zope.interface.implements(IFoo,)