Give VH items their own tree nodes and controllers

+ Add Controller.InsertNode
+ Add VHController
+ Add an icon for "vh"
Report EntryChunk packing errors to the user
Add controllers for the remaining entry types

+ Add T4EntryController
+ Add EntityEntryController
+ Add SoundEntryController
+ Add WavebankEntryController
+ Add SpeechEntryController
+ Add EntityController
Organize controller source files into directories
Make entry and chunk loader registration automatic

+ Remove Registrar