Add support for serviceScope element in PI file

[magicbadger]

During PI file generation, the serviceScope element is largely ignored. And by largely, I mean totally.

This element is useful for clients that dont have the means to infer bearers on a PI file either from a URL, or DAB EPG binary signalling. This gives the ability to ingest the PI as a standalone document.

 <schedule creationTime="2014-04-11T01:20:00+01:00" originator="Global Radio">
 <scope startTime="2014-04-25T06:00:00+01:00" stopTime="2014-04-25T13:00:00+01:00">
   <serviceScope id="dab:ce1.c185.c479.0" />
   <serviceScope id="fm:ce1.c479.09580" />
   <serviceScope id="http://media-ice.musicradio.com/Capital" />
 <serviceScope/>

This will need to be supported in the following places:

• Python object support, adding bearers set to the schedule object. This will be used to collate bearers on the PI file.
• Encoding/Decoding of bearers to/from XML
• Encoding/Decoding of bearers to/from binary
• Support for serviceScope in test tools

If there are multiple bearers in the serviceScope, then bearers will need to be added to each programmes location element.
If there are no bearers against the location, inherit from the schedule bearers.
If there are bearesr against the location, these override, but at least one bearer should correspond to the schedule bearers. If not, there should be a warning.