[WIP] Add a new "installerless" server launcher.

[modmuss50]

This makes launching a fabric server just a matter of downloading a jar from the website or via a URl and launching it just like a normal minecraft server, without the need for an installer. This has a number of benfits:

• Easier to people who use server hosts that expect a specific jar name, no more messing with properies files and renaming 2 jars.
• Easier to automate as its just a matter of downloading a single jar file and running it, this will also help people that want to containerise the server. (Might be worth having an official docker container?)
• Partly offline with no reliance on fabric's server.

Meta will provide an API to download a jar that has been marked with the minecraft server url/hash/name and the correct intermediary mappings. The website will present this in a user frieldly manner.

The old server installation method will still be supported for the time begin. Possibly start phasing it out by removing the option from the installer GUI but keep the CLI?

[modmuss50]

I will setup the building of jimfs with guava shaded/repackaged in.

[liach]

And you can probably consider proguard shrink the shaded guava

In addition, shading an updated guava will allow us to update jimfs, which is quite desirable.

[modmuss50]

Going to move this into the installer, the same idea but will mean there is really only 1 load of installer logic, smaller jar files to download (easier to batch upload or generate on the fly)