Avoid absolute URLs, profiles directory is always relative to
documents. Assume profiles to be based in the documents root
unless directory is != nil.
Given that, starting from iOS 8, the documents location can change
from time to time, could this fix#19?
- Store only profile key/metadata into service.
- Map profiles by (context, id), context being either provider
or host.
- Initialize cache with a placeholder profile, lazily load full
profile (e.g. after opening profile).
- Only serialize non-placeholder profiles (opened once).
- Do not load full profiles for organizer listing
WARNING: always load active profile as non-placeholder.
