Change 'channels' field to 'channelGroups' to more properly reflect its contents
Alter name of channelGroup list from 'channels' to 'channelGroups'
Add new regional/timeshift fields to Channel for additional variant info from the PA.
Add helper method related to countries to ChannelGroup.
Rework history output for simple model, and tidy up Simplification
 - Change channelNumber param to String
 - Add new ordering for channelNumbers. Ordered with non-zero prepended strings ordered in numerical order, followed by zero prepended strings, ordered in numerical order
Refactor of simple model around channels. Ordering for simple-model channel numberings moved to separate class.
Test added around ordering.
Modify equals method on ChannelNumberings
Minor tweaks to channels model after refactor of persistence layer