* Add guard against ServerBase.Dispose() being called multiple times. Add reset event to avoid Dispose() being called while the ServerLoop is still running.
* remove unused usings
* rework ServerBase to use one collection each for sessions and ports, and make all accesses thread-safe.
* fix Logger call
* use GetSessionObj(int) instead of using _sessions directly
* move _threadStopped check inside "dispose once" test
* - Replace _threadStopped event with attempt to Join() the ending thread (if that isn't the current thread) instead.
- Use the instance-local _selfProcess and (new) _selfThread variables to avoid suggesting that the current KProcess and KThread could change. Per gdkchan, they can't currently, and this old IPC system will be removed before that changes.
- Re-order Dispose() so that the Interlocked _isDisposed check is the last check before disposing, to increase the likelihood that multiple callers will result in one of them succeeding.
* code style suggestions per AcK77
* add infinite wait for thread termination
