Extract log parsing to a own library

[ChillerDragon]

There should be one reusable library that abstracts away teeworlds log parsing. It should support multiple formats like ddnet, 0.6 and 0.7 and give one versioned interface for working with all of them. It should be sans io and well tested so it can be used for anything.

That could then also serve as a base for any kind of server modding not only how it is used in this repo.

The api should offer callbacks like:

on_message() -> every log as string
on_player_join() -> player info
on_unknown_message() -> same as on_message() but only if the parser doesn't know it