Reliable message preview 10

This is a significant new release and contains major new features and bugfixes. I recommend everybody using libyojimbo update to this release right away. Please be aware that the API is slightly changed in this release.

New features:

1. Per-client allocator, packet and message factories on the server. This is a security measure to make sure that clients cannot spoil or exhaust a resource shared with other clients, but can only exhaust their own resources. When a client's resources are exhausted on the server, that client is disconnected.
2. Security fix so that replay attacks with stale connect tokens can be quickly discarded with AEAD signature check vs. having to decrypt the whole connect token just to find out the timestamp is old. This is a much faster reject because signature check is significantly faster than decrypt.
3. Replay packet attack fix. Malicious clients can no longer sniff your connection packets and replay them to try to corrupt your internal connection state (eg. reliable messages, uint16_t sequence # after wrapping). This would have been a hard attack to pull off due to timing, but it was possible. Now it's impossible.
4. Client can now pass multiple servers in to secure and insecure connects. Client tries each server in turn, up to MaxServersPerConnect in an array, until the first connect succeeds. This is the intended behavior for connecting via connect token returned from the matcher, and now it's as simple as passing an array of server addresses to the connect function.
5. Expanded test coverage and bugfixes. I've added test coverage for client reconnecting, switching between insecure connect to secure connect and back to insecure, plus a bunch more stuff. In doing so I found many issues, mostly caused by rare situations or use cases like reconnecting that weren't picked up by previous test coverage.

The nature of these new features and bugfixes required changes to the API. Please refer to shared.h and client.cpp, connect.cpp and server.cpp for examples showing how to setup yojimbo client and server classes with the new API.