Refactors creation of objects

Removes the unucessary concept of adapters. Node are the adpater
itself. Synchronizer really becomes the central part that "holds" all
node, like in previous verison of liboncilla. But here it holds the
implentation object, rather than the raw API objects.
HWOncillaBackend contains no other logic than creating the components,
and is just a simple entry point.