Force iCloud calendar events to be shown 1 hour ahead

## Problem

iCloud for a while now has always shown events on its calDAV backend to be 1 hour behind its actual 'native' (to Apple devices and services). I quite literally missed a class because not even Fastmail's iCloud integration compensates for this :(

## Proposal

Either get EDS devs to consider adding the ability set time offsets for specific DAV providers, or figure a way to do it specifically on elementary OS. This would mean that Calendar interacts with, and displays times, through the 1hr offset exclusively with detected iCloud accounts.

## Prior Art