Implement audio backend configuration option (#1325)

* Implement audio backend configuration option

* Use OpenAL by default

* Increment version number in config.json

and add 30px to the height of the settings window

* nits

* capitalise audio backend names

Ryujinx.Common/Configuration/AudioBackend.cs

@@ -0,0 +1,9 @@
+namespace Ryujinx.Configuration
+{
+    public enum AudioBackend
+    {
+        Dummy,
+        OpenAl,
+        SoundIo
+    }
+}