Pre-compiled proxypass jar is included instead of source

Currently a pre-compiled proxypass jar file is included in the repo. (in /data) It would be nice if the source could be directly included so that we can see the source/differences if there are some and be part of the build process (or pulled in via a submodule or if it's just an unmodified [CloudBurst/ProxyPass](https://github.com/CloudburstMC/ProxyPass) from their build server on start?)