Fix multiplayer quick start, adjust cut off text, and other minor fixes

[StenAL]

This set of commits fixes many minor things:

• Multiplayer quick start no longer deadlocks the client. Now it just joins the lobby.

Before	After

• The "Create a new game" multiplayer text is no longer cut off

Before	After

• Right clicking players in lobbies now opens a pop-up menu with some actions.

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• The server now handles error-debug, end, and lobby command packets

  • error-debug is sent by the client when it crashes and includes an error message and the last commands sent/received. This is useful for debugging. It also necessitated increasing the maximum client package size to 2000 bytes since errors can be long.
  • end and lobby command are no-ops

• Verbose server logging can be enabled with a flag to see outgoing packets. This is useful for debugging.

• The username regex no longer prevents empty strings as usernames. These are handled by the server and users are assigned a name like "~anonym1111"

• Some networking classes are renamed for better clarity

• Some unused classes and meaningless JavaDocs have been removed

[StenAL]

Hey @PhilippvK, pinging you in case you haven't seen this PR. I have some other changes ready to publish but would like to get this PR in first.

[PhilippvK]

@StenAL When the PR was posted I was traveling and could not try out the changes myself. Sorry for the delay! In the meantime I was able to check the changes and think we can get this merged soon.