This adds the actual switch to turn on Hardcore Mode to the settings tab of the Achievements dialog. It is accompanied by a large tooltip warning explaining what it does and when it can be enabled.
The switch is only enabled to be turned on when no game is running, so that games are started in hardcore mode and can only be loaded via the console's memory card, as in the original hardware. Hardcore may be turned off while a game is running, but cannot be turned back on until the game is disabled.
The toggle trigger for hardcore mode also automatically disables the settings that are not allowed during hardcore mode.
Finally, the original flag in AchievementSettingsWidget to set whether things are enabled in hardcore mode (primarily Leaderboards) is replaced with the actual Hardcore Mode setting.
AchievementSettingsWidget is a dialog widget in AchievementsWindow for handling RetroAchievements settings in the user interface. This class contains the physical layout, widget connections, load/save functions and button responses. AchievementsWindow now has a tabbed list that this is inserted into; other tabs will be in a later pull request.
LillyJadeKatrin