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.
AchievementsWindow is the dialog box that will eventually contain the settings and progress data for RetroAchievements on Dolphin. This adds the barebones dialog, and connects it to MainWindow's MenuBar.