Simplify tests by loading modules components
Simplify tests by loading modules components

It the previous commit, @lmignon added the possibility to load all
components of an addon in a Component Registry.  This commit takes
benefit of this feature to simplify the existing tests and to add a base
test case for the Connector (that loads all components of 'component',
'component_event', 'connector'). It can be used in implementations using
the connector.

OCA/connector,OCA/connector