Combine client and server into single repo

[plaza-in-a-heatwave]

Several benefits of combining the repos:

• Combined build and release scripts
• some items can be shared across both client and server e.g. constants, packet definitions, auto updater
• issues and ticketing are made much more straightforward

Considerations:

• gradle scripts
• git merge unrelated histories

[plaza-in-a-heatwave]

Done in 48e8e4a64aa4de3719dabbbf7994e49b9fbf98e9