I read somewhere that the "Synchronize" item on the module's context menu should update the IDE's settings based on the build.gradle file.
Ok, so in the latest version of Android Studio 0.1.3, they've added a Gradle project refresh button next to the other Android specific buttons in the toolbar. Make changes manually to the build.gradle files and settings.gradle and then click this button. It should configure and refresh your project settings based on the gradle files.