Add string interpolation conversions for other common .NET APIs

[DustinCampbell]

It'd be great to be able to apply the "Convert to String Interpolation" to .NET APIs other than just String.Format(). For example:

• Debug.WriteLine(string, params object[])
• Console.WriteLine(string, params object[])
• StringBuilder.AppendFormat() (even though this causes an allocation)

[pharring]

Add to the list TextWriter.Write and TextWriter.WriteLine

[fsateler]

Or user-defined methods as well.

[DustinCampbell]

@fsateler, Do you have a proposal for how that might be detected? Requiring a parameter of type string and a parameter of object[] seems too permissive.

[fsateler]

@DustinCampbell I think the only reasonable way is to require annotation with an attribute. This would also allow formatters that require extra parameters:

 [FormatStringConsumer(FormatStringParameterNumber = 2)]
 void WriteToDevice(Device d, string format, params object[] arguments) { ... }

[DustinCampbell]

Nice idea! Should probably be a separate issue though. Added #21 to capture this.