Add CD icons in sound picker
Show custom styles in settings

Now styles created by plugins will show up in the preferences.  Also
moved the style selector to the top of the dialog and made it a proper
dropdown. Minor refactoring (renaming properties) on StyleGroup class
Hotfix for keyboard nav in prefs

Fixed tab order, and set cancel button so user can cancel dialog by
pressing esc.
Merge pull request #27 from fatcerberus/master

Sound picker icons, custom styles in prefs