Set log level DEBUG for unittests
MultiDiskAdaptor: Use std::unique_ptr for DiskWriterEntry and DiskWriter

MultiFileAllocationIterator is also rewritten so that it does not
requre copying DiskWriterEntry objects.
MultiDiskWriter: Rewrite resetDiskWriterEntries() using simpler algorithm
Use std::unique_ptr for FileAllocationIterator
AbstractSingleDiskAdaptor: Use std::unique_ptr for diskWriter_
DefaultPieceStorage::initStorage: Clean up
Use std::unique_ptr for IteratableValidator
Use std::unique_ptr for CheckIntegrityEntry and FileAllocationEntry
DownloadEngine: Use std::unique_ptr for checkIntegrityMan_, fileAllocationMan_
DownloadEngine: Use std::unique_ptr for RequestGroupMan
MultiUrlRequestInfo: Remove virtual from dtor
Use CXX11_OVERRIDE
DownloadEngine:: Use std::unique_ptr for webSocketSessionMan_

Notifier::addDownloadEventListener now takes pointer to
DownloadEventListener. Session holds unique_ptr to
ApiCallbackDownloadEventListener object.
DownloadEngine: Use std::unique_ptr for dnsCache_
DownloadEngine: Use std::unique_ptr for btRegistry_
BtRegistry: Use std::unique_ptr for BtObject
Refactor MultiUrlRequestInfo ctor

StatCalc creation is moved to MultiUrlRequestInfo.  The summary output
is done only when PREF_QUIET is false and it is always to
global::cout(), so remove summaryOut_ and just use global::cout() in
that case. Also use std::unique_ptr for statCalc_ in DownloadEngine.
DownloadEngine: Use std::unique_ptr for eventPoll_
MultiUrlRequestFactory: Use std::unique_ptr for DownloadEngine
TrackerWatcherCommand: Use std::unique_ptr for trackerRequest_