Create an UpdateDispatcher interface to decouple Dispatcher and Updater components

[PaulSonOfLars]

What

This aims to address #119, allowing users to implement their own dispatchers with their own custom logic

Impact

• Are your changes backwards compatible? No - NewUpdater definition has changed, the Updater struct's Dispatcher field has been changed to be an interface.
• Have you included documentation, or updated existing documentation? Yes
• Do errors and log messages provide enough context? Yes