Semi-comprehensive linux port of the client.

[asier-ochoa]

General objective:

With this PR, sc4mp's client should work on linux and steam without having to mess around manually with the wine prefixes. Configuration files and data should be saved on ~/.local/sc4mp-client by default. Applying client plugins should be done via symlinks to the Documents/Simcity 4 folder. The final goal is to be able to distribute the client in such a way that it should run ootb on common linux distributions. (Maybe distribute on the AUR if permission is granted?)

Goals:

• Monitor SC4's process as seamlessly as it is on windows
• Automatically launch the game from either a specified wine prefix or directly from steam (watch out for flatpak steam)
• Symlinking of plugins to the Documents folder on the prefix
• Modifying the core logic of the client such that it accomodates these changes but doesn't affect current windows functionality
• Implementing the "first_time" user logic so that linux users can specify their paths. Attempt to implement for windows as well.

[asier-ochoa]

This issue regarding launching a steam version of SC4 on windows could be fixed by using steam's browser protocol. This functionality is partially in this PR (implemented here). Could try to add it to the windows function for launching sc4.