Optimize ProfileManager in several ways:
- Refine control over objectWillChange
- Observe search separately
- Store subscriptions separately (local, remote, search)
- Fix multiple local updates on save/remove/foreground (updating
allProfiles manually)
- Update the library with more optimized NE reloads
- Cancel pending remote import before a new one
- Yield 100ms between imports
- Reorganize code
Extras:
- Only use background context in provider repositories
- Externalize tunnel receipt URL, do not hardcode BundleConfiguration
- Improve some logging
Self-reminder: NEVER use a Core Data background context to observe
changes in CloudKit containers. They just won't be notified (e.g. in
NSFetchedResultsController).
Fixes#857
