Remove defaultValue semantics from the interface. This would mean that null interpretation is dynamic in nature and can change with each call to get. However, we implement using a static value of -1 and don't distinguish between a null and -1. Fix test cases.
Add explicit toString to int value (char + int -> string/int ?). Remove redundant char casts.
Remove explicit char to string conversion
Fixed vanilla TernaryTrie implementation. Use char key, single int value and plug into interface.
Remove TernaryTrieImplicit. Doesn't seems useful to move forward with.