Change "Unknown" to "EID" in Entry
Properly load and save music entry info items
Change export menu option text
Add incomplete VAB to DLS conversion

+ Add VAB
+ Add VHProgram.ToDLSInstrument
+ Add VHTone.ToDLSRegion
+ Add Length to RIFFItem
Add DLSFilter to FileUtil
Add FindEID to EntryChunk and NSF
Add FindEID to EntryController
Add music entry menu options to export linked VABs
Simplify controller menu handlers

+ Add ControllerMenuDelegate
Use an exception for GUI menu errors

+ Add GUIException
+ Handle GUIException in Controller MenuItem click events
Implement "Export Linked VAB"

+ Add VAB.Save
+ Add VAB.Split