Removed unneeded extra locking, added RequeueCause to the requeue event.

Cleaned up suspicious looking (missing) locking in ApplePushChannel.cs
Fixed build config
Added logging facade, additional log messages in APNS.
Added debug level to allow for repetitive messages.
Fixed re-entrancy issues on timers.
Corrected potential infinite loop in Dispose().
Possible fix for PushSharp #157, dropped keepalive time to 20 minutes to compensate for crappy NAT devices.
Merge branch 'master' of https://github.com/bmatson/PushSharp