go model codegen produces unexpected behavior for enums

[boynton]

The generated SymbolSet() method on enums returns an array of the symbol names, indexed starting at 1 (the 0'th entry is the empty string). Should just be the set, without that empty string.

This may imply that the enum values should start at 0, not 1.

This would be an incompatible change.

[boynton]

This does allow the distinction of a default value vs none, however.