Add activity icon and make it a Share activity
Clean up business authentication so also uses cached (not persisted) auth and lazy init/auth.
-Businesses don't know either the auth token OR the note store URL until auth is complete, so allow ENNoteStore client to
 get both from its subclasses, lazy-creating an EDAM client as required.
-Business auth in practice expires in about an hour, so don't put that on disk in the credential store along with the
 longer-term OAuth tokens. Keep it alongside the linked notebook credentials in the auth cache. This cache is currently
 not persisted anywhere, and will be rebuilt every app launch lazily for each access.