Add DisplayName in TypeReference helper

[andry-tino]

Base helper TypeReference has Name and FullName. Problem is that base level factories are using FullName which is good for ScriptSharp definitions, but not for normal translation.

1. Add DisplayName to TypeReference.
2. Have factories always use DisplayName when invoking TypeReference.
3. Make DisplayName return Name in Rosetta.AST.Helpers.TypeReference.
4. Make DisplayName return FullName in Rosetta.ScriptSharp.AST.Helpers.TypeReference.