Fr: better icloud document storage support

there are two things i found missing here.

first, add an iCloud Permissions option to the macos exporter. it should add the same entitlements as the ios version (eg, com.apple.developer.icloud-container-identifiers, com.apple.developer.icloud-services, and com.apple.developer.ubiquity-container-identifiers)

second, the default container identifier on the ios side is iCloud.$(CFBundleIdentifier). ideally this would use the base juce bundleIdentifier since $(CFBundleIdentifier) can be overridden in the ios/macos exporters.

this ended up being pretty easy: