ParseAssemblyInfo does not support verbatim string literals

### What You Are Seeing?

AssemblyInfo properties are being omitted if the are written using verbatim string literals

e.g:

```
[assembly: AssemblyProduct(@"Foo "to" the bar")]
```

Will result in an `AssemblyInfoParseResult` with an empty `Product`.
### What is Expected?

That the `AssemblyInfoParseResult` should contain `Product` with value of `Foo "to" the bar`
### What version of Cake are you using?

0.16.1

Locate the ParseAssemblyInfo entry point and reproduce the AssemblyInfo example from the issue. Trace how the AssemblyProduct value is parsed, then verify that the resulting AssemblyInfoParseResult contains Product set to the expected value for a verbatim string literal.

Written by the indexing model from the issue text.