Added continuous-build scheme for iOS

For use by the Xcode continuous-integration bots, which require a
shared scheme to use.
Just removed an unused internal method.
Fixed ReplicatorManager not detecting replications on 1st launch of app

Fixes #170
Use streaming JSON parser for _changes feed
Added -Woverriding-method-mismatch warning flag

…and cleaned up the things it caught.
An FMDB optimization (for binding objects to query columns)
Implemented rev-tree pruning.

During database compaction, excessively-deep revision trees will have their oldest revisions removed
entirely. The depth limit can be configured as CBLDatabase.maxRevTreeDepth.
Fixes #118.
Oops, added missing vendor/yajl/build/yajl-2.0.5/include dir
Added polling mode to pull replicator

Add property “poll” to a continuous pull replicator’s options.
Value is poll interval in ms; minimum 30000.
Improved documentation of -[CBLView setMapBlock:reduceBlock:version:]

In particular, the meaning of the return value was previously undocumented.
Fix race condition deleting a persistent replication

Fixes #176
Added isGone property to CBLDocument and CBLRevision

This indicates that a document is no longer available because it’s been removed from available channels,
or has been deleted. (That is, it detects a “_removed” or “_deleted” property.)
Fixes #29
Fix ref-cycles by making CBLRevision.document a weak ref

Fixes #177
Update FMDB for shared-cache mode and better busy retry behavior

* Use SQLite3 shared-cache mode, to save memory with multi-threaded
  access.
* FMDB now treats busyRetryTimeout as a time interval not an iteration
  count, and uses a more realistic interval between retries.
Fixes #178, I think.
Speed up database creation by wrapping it in a SQLite transaction
Allow public objects to be bound to a dispatch queue

By setting the CBLManager’s dispatchQueue property, the manager and the
objects it creates will run on that queue instead of the thread it was created on.
Most importantly this means that callbacks like notifications and model autosaves
will be scheduled on that dispatch queue.

Also added the related method -[CBLDatabase doAsync:] which runs a block
asynchronously on the database’s thread or dispatch queue. This can be called
from any thread.
Added -doAsync: to CBLManager too, for completeness.

To avoid confusion I renamed the existing -asyncTellDatabaseNamed:to:
to backgroundTellDatabaseNamed:to: since it has a different purpose.
Removed broken link to automated build. Other minor edits.
Oops, took out some temporary logging calls
Updated FMDB: Use sqlite3_busy_timeout to handle busy/locked errors

Also increased busy timeout to 5 seconds.