Replace error loggers in updater+dispatcher with error funcs, for improved flexibility

[PaulSonOfLars]

What

Improve error handling flexibility in the Updater and Dispatcher by providing error funcs instead of simple logs.

This should allow users to panic and close their program if necessary.

Impact

• Are your changes backwards compatible? No - some method and struct signatures changed to apply new changes. Overall minor.
• Have you included documentation, or updated existing documentation? Y
• Do errors and log messages provide enough context? Y

[ALiwoto]

I'm seriously waiting for these changes to be merged :) Really good job!