- Added getter Fields() for node.FieldMap.
- Found a few more label references to convert from string to
interface{} as FieldMap key in doclayer.go.
- Added convenience method node.IdToField() in doclayer.go
- FieldMap and FieldList were incorrectly represented in types.go as
pointers, they are now map and slice aliases respectively.
- Found error in use of ValueLocationBytes(); a MasterCatalog file
record has an extra LBTYPE_SIZE bytes compared with a Zapmap record.