feat(liblobby): handle multiple newline separated commands

[tetrisface]

This code aims to speed up lobby setup by letting the user submit multiple commands like battlesettings etc in a single input message. Some samples:

Tested:

• [x] standard commands
• [x] long tweakdefs (bit of a freeze in my dev environment on paste)
• [x] empty values
• [x] broken line copies

[tetrisface]

To prevent game start crash I added support for handling tweakdefs that use "legcomlvl"