"Launcher"

This MR introduces a GUI. The "Launcher" (it is not a launcher, it is basically the game) has a server list, you can specify your server and connect to it. Once everything is "ready" (=We received our spawn location), The "Launcher" minimizes itself and opens the actually game. This will happen is almost 0ms after being ready, because everything important happens in the Launcher. The Launcher downloads, loads, etc everything while waiting for the user to login or choose the server.

ToDo:

• Improve and fix design issues
• Account management (GUI, check for valid account in background) e622571a
• Session management (= active connections to a server): 744189c7
• Settings: 652e0c30
• Texture, mappings, etc downloader
• Improve start time (3s is a lot (1s is account checking)
• First server appears twice (pings are twice, ...) 8f5365f7

Changed/Fixed:

• 1.8 chunk reading
• Network bugs with the ArrayList (queue), replaced with a LinkedList
• Refactored Network.java
• Support for all versions ans snapshots between 1.15.2 and 1.16.2 8901f388
• mappings generator