RCON lacked encryption, added AES-CTR encryption on RCON frames. Slightly adjusted protocol to take this into account (sending nonces, encrypted data itself, etc).
- Upgraded hashing algorithm to SHA-512, and store the raw hash instead of a string copy, which is way cheaper to compute and compare.
- Only ever close sockets once in CRConServer::SetPassword().
- Made the game server & game client RCON singletons static.
- Added calls to gracefully shutdown RCON server and RCON client on Engine/SDK shutdown.
- Added more prints so RCON user knows when its shutdown, or when their password change is in effect, etc.
- Fixed bug where we could tokenize an empty string when we dispatch a console command.
