Multiple instances

I've sat on these changes and never issues a PR to get the thoughts going on multiple Recurly instances with .Net.

Notable changes are how the web/app.config file is setup and methods are called. Most of which require an instance name to map to the proper api credentials.

Recent changes are to make the projects more friendly once forking/downloading the code.

While this is a PR, I'd totally understand if declined since it is likely abnormal to have more than one instance.