Made newRev.parentRevID work in a validation block

Also, newRev.revisionID will consistently be nil for a newly-added revision,
instead of incorrectly being the parent’s revision ID. (It would be best if it were
the actual new revision ID, but that hasn’t yet been computed by the time the
validation block is called.)
For #233
Fixed FMDB memory leak, and removed a now-unused variable.

Leak was introduced in prior FMDB update on 1/24 (c2f6d7e).
Fixes #263.
CBLDocument.currentRevision should be nil after deleting doc

Fixes #265
Draconian thread-safety check for FMDatabase

People keep trying to call CBLDatabases on multiple threads and don’t understand the generic “database in use”
warnings. So I put in an explicit same-thread test that triggers an unblockable assertion failure with a very explicit
message about CBL thread safety.
Made CBLUITableSource.m more portable

Removed usages of MYUtilities so the source file will build in an external app project
with no dependencies other than public Couchbase Lite API. This helps developers who
want to copy the source to extend the class’s functionality.
Extended draconian thread-safety check to support dispatch queues.

If the CBLManager.dispatchQueue property has been set, databases will check for the
correct queue, _not_ the correct thread.
Oops, fixed compiler warning/error introduced in last commit.
Support for transforming/encoding revisions during replication

This enables encryption of documents on the server, for example.
Based on a patch from Alan McKean; thanks!
Fixes #253
Fix crash caused by premature dealloc of CBLMultipartDocumentReader

See #266
Update README.md

Removed the (out of date) summary of the build instructions. Let's just have one set of real instructions, on the wiki.
Replication transformation tweaks

* Assert that the transformation block didn’t alter the “_revisions” property.
* Edited the doc-comments to clarify that all _-prefixed properties have to be preserved.
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.