Pydvbcss

* Bugfix: Initialiser for `CIIServer` class to avoid corruption of default value for `initialCII` if a 2nd CII server is instantiated
* API addition: Added `copy()` methods to all classes representing JSON messages.
* Bugfix: `TSClient` class did not correctly handle when contentId is null
* Bugfix: `examples/TSClient.py` now exits when the connection is closed.

* Completed support for uploading packages to pypi to enable installation using `pip`
* Bugfix: setup.py was not tracking same version number as in `VERSION` file.

* API change: Modified API for TimelineSource for TS Servers to allow for situations where it takes time to begin extracting a timeline at the server.
* Docs: Switched to referring to spec as ETSI 103 286 now it is published by ETSI
* Docs: Updated to reflect API changes
* Docs: General minor fixes
* Bugfix: CIIServer disconnect callback failed due to wrong number of arguments
* Bugfix: Incorrect use of `"presentationStatus"` CII property in examples. Should have been a list, not a string. Also added a check to trap this.
* Bugfix: Some command line arguments being ignored in `examples/TVDevice.py`
* Bugfix: Wallclock time printed in wrong units in `examples/WallClockClient.py`

* API change: Added ways to extract dispersion and worst-dispersion information more usefully from wall clock clients.
* Tests: Minor unit test improvements

* Bugfix: Fixed problem in `setup.py` that meant when pydvbcss is installed it could not be imported into another python program
* Bugfix: Fixed incorrect content ID URLs used in CII Server example
* Docs: Various documentation improvements
* Tests: New unit tests