Refactoring

* add overflow marker "…" to LoggingInputStream
* split the populate() methods
* always close cursors (resolves #120)
* introduce LocalStorageException and its subclass RecordNotFoundException and catch RemoteException earlier
* split synchronize() method into phases
* commit after every added/modified record (obsoletes MAX_UPDATES_BEFORE_COMMIT)
* read contact photos from (high-res) asset instead of the thumbnail blob (resolves #121)