Rename constructor name/type to constructor tag which is more accurate.

- Rename "constructorNameModifier" to "constructorTagModifier".

- Rename "ObjectWithType" to "TaggedObject".

- Rename "typeFieldName" to "tagFieldName".

- Rename "defaultObjectWithType" to "defaultTaggedObject".
Renamed fieldNameModifier to the more accurate fieldLabelModifier
Renamed nullaryToString to the more accurate allNullaryToStringTag
Fix test-suite to use the new encoding Options terminology