Sound system improvements

- Fix sound ACP uploads
- Display soundpack names with sound files
- Soundpacks can have sounds with identical names
- Link sounds during build step
- Generate map of sound name to file name during build step
- Change how soundpacks work. It's now done via a field in plugin.json

src/plugins.js

@@ -32,6 +32,7 @@ var middleware;
 	Plugins.libraryPaths = [];
 	Plugins.versionWarning = [];
 	Plugins.languageCodes = [];
+	Plugins.soundpacks = [];
 
 	Plugins.initialized = false;