Switched to redis/postgres, major refactoring

- loginMetadata is passed to shards through redis now
- shards announce they're alive via redis.AnnounceShard() which just
  populates a hashset keyed 'shards'
- login servers grab the 'shards' hashset and randomly picks a shard to
  pass the player to (for now)
- ./service shard && ./service login
- Many new environment variables, check config/config.go for more info.
  or for a tl;dr just read the Dockerfile for the required ones
- Shard and login services now run in different processes ! (and
  containers?? wooaaah)

build.sh

@@ -1,5 +1,5 @@
 #!/bin/sh
 
 mkdir -p bin
-CGO_ENABLED=0 GOOS=linux go build -o ./bin/server
+CGO_ENABLED=0 GOOS=linux go build -o ./bin/server ./cmd
 echo 'Done'