Change name of channelGroups collection from 'channels' to 'channelGroups'
Refactor of channels ingest, plus ingest of new regional/timeshift fields, and ingest of highDefinition and mediatype fields.
Also now ingesting youview channel aliases where provided by the PA
Ensure response has character encoding and content type set, to prevent dodgy characters from incorrect decoding of UTF-8
 - Change region uris & aliases to be PREFIX + platform id + "-" + region id.
 - change date serialisation to output in format yyyy-MM-dd
 - change simplification to output correct historical blocks
 - channel.startDate now on top level of channel rather than in history block
 - channel tests updated to use new method name and new region uris/aliases
 - Change channel number to string, to cope with cases such as sky using both channel 101 and 0101.
 - Modified logic around history to reflect that multiple channel numbers may link a given channel/channelGroup pair at a given time.
 - Added initial version of test to check behaviour of channel numbering simplification
Refactor of Channel Number simplification. Modification of condition around filtering numberings when the history annotation isn't specified
Rework testing for channel numbering simplification, and resulting modifications to simplification code.
Major refactor of the channels ingest, to improve speed and to try and eliminate situations where incomplete data is written