Modified user agent for calls coming out of Sync Manager

App type will be NativeSmartSync or HybridSmartSync
(In line with the work we did in 2.0 for smartsync.js, the user agent for calls coming out of smartsync.js have HybridSmartSync or WebSmartSync as app type)
Also, do you see any value in explicitly setting this value in the native `AppDelegate` methods as well, just for visibility?