Rename Obj-C classes from 3rd party libraries, like DDLog & HTTPServer

Since Obj-C has a global class name table at runtime, there will be
trouble if a process ever contains two classes with the same name (even
though we're careful not to export symbols we don't need to.) This has
led to trouble in apps that link both with CBL and with libraries we
use such as CocoaLumberjack and CocoaHTTPServer.
To fix this, I've added some #defines in the prefix header that rename
all the 3rd party classes  to have a "CBL_" prefix.
Fixed CBLManager_Close test case

It was using the shared instance of CBLManager, which made the results
unreliable, causing occasional exceptions.
It tested 'out' error parameters that actually have undefined values.
It deleted a CBLDatabase whose manager had already been closed.
Fixed bogus SSL untrusted-cert errors with self-signed certs

Some RemoteRequest objects weren't getting their delegate property set.
This caused them to not check the list of explicitly authorized root
certs during SSL handshakes, which means they'd reject self-signed
certs (or other certs without globally recognized roots.)