[AE][GUI] Add Audio category to System Information GUI window and popula...

...te with current AudioEngine audio device capabilities enumeration results.

This PR aims to present the capabilites of the currently selected audio device in the System Information GUI window as we currently do with other hardware info.

This is the result of the code on my machine with an HDMI device selected: http://i45.tinypic.com/2n8wgnq.jpg

The data is derived from the sinks EnumerateDevicesEx() method.

As written, it calls the loaded engine and thus requires similar methods to be added for CA. It would be great if Gimli, Davilla or Memphiz could comment on whether useful information can also be returned from CA. If not we can make it specific to SoftAE/Linux/Windows.

There is limited space available in the window - as shown and written there is just enough room to describe the current passthrough device. If the window were scrollable we could add the current PCM/analog device info a well. Perhaps Jezz_X can comment on that possibility.

The goal is to provide the user with enough user-friendly info on their device(s) capabilities.