List -> IList wherever possible, ConvertAll -> LINQ Select, (automatic) formatting

We currently have a mutt codebase of `List` and `IList` types being used interchangeably, so this commit fixes that wherever possible, so we can derive any other type implementing `IList` from our methods.

`ConvertAll()` was used in `PlaylistsApiHandler.cs`, but this method is from .NET 2.0, and LINQ `Select()` is a better choice now: http://stackoverflow.com/questions/1571819/difference-between-select-and-convertall-in-c-sharp

My vim automatically removes any trailing whitespace, so you may notice that as well.