Oops, broke the build of the iOS demo app.
CBLReplicator should suspend, but not stop, when iOS app is backgrounded

This functionality used to be provided for persistent replications by
the CBLReplicatorManager. It’s now built into CBLReplication itself.
CBLReplicator: Make more ivars private, move them into the .m file

This limits the ability of the subclasses to use them incorrectly.
Just being paranoid.