fix string unquoting upon parse

[Aaronontheweb]

closes #190

[Aaronontheweb]

So this isn't a bug with the parser - it's an API change. The original HoconValue.ToString() method return the unquoted string, but we also didn't have proper support for merging and flattening of HOCON back then. Now we do, but the consequence is that the raw HOCON is what needs to be exposed during those ToString operations on that HOCON.

Thus, we also have the HoconValue.GetString() method - which returns the human-usable value that we are likely looking for inside our applications which consume HOCON. I've updated the XML-DOC comments to reflect this little gotcha, but otherwise it's not a bug that can be easily addressed without breaking something more nasty like object merging.