Investigate potential issue with verbatim strings in javascript.

[cbengtsson]

From code-review:

This change makes verbatim-string phrases preserve literal newlines (instead of converting them to the two-character sequence \n). Downstream code that embeds phrase keys into generated JavaScript needs to escape these characters; otherwise a phrase key containing a newline or quote will produce invalid JS. For example, MN.L10n.JavascriptTranslationMiddleware/FileTranslator.cs builds x["{key}"] = ...; for plural phrases without escaping key. Either ensure key is escaped/JSON-encoded there, or keep parser output normalized to a representation that is safe to embed.

See: #186 (comment)