Support CBOR serialization

[VigneshVSV]

From node-wot perspective, it was recommended by the community to try CBOR serializer for faster than JSON serialization.

Especially, this may be supported property-by-property basis & set the content type headers correctly just for the particular property. Before all that, it is useful to start supporting CBOR as a general serializer itself.

Possible steps involved

• Find a C/C++ supporting CBOR serialization implementation
• Overload BaseSerializer and add dumps and loads methods, type replacement registration, allowance for a separate hook which accepts types that are not by default seriliazable
• do speed tests and compare with other serializers, there is some boiler plate code here. Especially numpy types must be considered.
• test RPC operations & events (test_rpc.py, test_events.py)
• test support from Thing's init
• update content type for HTTP if it is used for thing.http_serializer