Initialize CBReplication.status to ‘offline’ in the -start call

This makes tracking the status easier. Before this change it would stay at ‘stopped’ for a little while
until the background replicator thread started up.
Fixed target OS requirements

* Some iOS targets were still set to iOS 5; updated everything to iOS 6.
* Updated Mac OS target to OS X 10.8.
* Added a (strong) annotation to a dispatch_queue_t property in CBLManager.h
to avoid a warning with OS X 10.8+.
* Updated ErrorUtils in MYUtilities to stop using a deprecated function.
Fixed crash in WebSocket-based _changes feed handling an HTTP redirect

Fixes #246
Minor tweak to unit test to suppress static-analyzer warning

Just marking a variable as unused.
Added unit tests for CBLMultipartDocumentReader, including gzip support
More MIME gzip encoding unit tests
Removed CBLReplication.propertiesTransformationBlock from public headers

The API hasn’t been through review, and it’s almost certainly subject to future change because
it doesn’t support attachments. We’ve decided it shouldn’t be exposed in a public header yet.
(See #251)

Clients can keep using it but they’ll need to declare it themselves, like:

@interface CBLReplication
@property (strong) CBLPropertiesTransformationBlock propertiesTransformationBlock;
@end
Fixed compiler error in Release build
Merges with upstream
Merge branch 'master' of github.com:mz2/couchbase-lite-ios