Align KATCPSensor listener callback API with katcp.Sensor

also:

Improve KATCPSensor listener callback mechanism to properly deal with methods
KATResourceClient implementation WIP
WIP
Merge branch 'master' into implement-KATCPResource
WIP
Passing smoke-test WIP
Fix KATCPSensor.set_sensor_strategy, other fixes, more smoke-test progress
Working basic sensor functionality
More or less working requests
Merge branch 'master' into implement-KATCPResource

Conflicts:
	katcp/inspecting_client.py
Add tests and minor fixes to inspecting-client

- Add inform-hook test, some other inspecting client test cleanups
- Correct inform handler: 'interface-change' to 'interface-changed'
- Add test for handle_sensor_value
- fix version test race condition
- Add tests for new inspecting_client connect-callback
  and factory functionality
Further addressing of PR43 comments
Merge pull request #43 from ska-sa/implement-KATCPResource

Implement katcp resource
Merge master into inspecting-client-state-loop