Reference: #91

Aliasing and function shadowing in the original `types` package should prevent most provider developer changes. The main exception is the newer type-specific `Typable` and `Valuable` interfaces were moved without a type alias. This should help developers find the necessary interfaces for custom types next to the base type implementations.

The underlying implementation of the primitive types (`BoolType`, `Float64Type`, `Int64Type`, `NumberType`, and `StringType`) are now fully exported types instead of the unexported `primitive` type which was difficult to extend.

The underlying value type creation functions were prefixed with New and the value types themselves were renamed to include Value at the end. This should prevent rough edges with the `String` value type since it conflicted with the `String()` method and could not be directly embedded easily.