Remove core configuration from test configuration

- phpunit.xml: Removing DatabaseSuite from cakephp
- Use our own TestPlugin
Fix: incorrect variable to use for count()
Reset TableRegistry and configure required tables in setUp()
Enable AclNodesTable::node() to accept Entity object
Fix: call parent and include __NAMESPACE__ in 'through' setting
Fix AclNodeTest::testNodeAliasParenting
Fix AclNodesTest::testNodeActionAuthorize()