[adapters] move class EntityAdapter from cubicweb.view to cubicweb.entity
The adapter mechanism is not specific to the use of views. Moving the
class the cubicweb.entity makes this clearer.
Additional services
===================
In this chapter, we introduce services crossing the *web -
repository - administration* organisation of the first parts of the
CubicWeb book. Those services can be either proper services (like the
undo functionality) or mere *topical cross-sections* across CubicWeb.
.. toctree::
:maxdepth: 2
undo