Automate launcher profile patching

[raphtlw]

Currently, there is an ongoing need to manually pull the latest launcher profiles from Mojang and modify the files by hand. It would be a lot nicer to have a function which checks for major version numbers, parses the JSON files and modifies the files directly, without the need for user intervention.

One issue with implementing this is, the profile files are only downloaded by the official launcher when the user clicks the play button, which means there is a need for the user to click the button before we can modify the file. Since there is no way to know when the launcher is done, and there is no way to stop the launcher from launching the game after the download is complete, this will be a tricky problem to tackle.