Fix Bug and Script Encoding

* All: Changed the character encoding of PowerShell scripts from Unicode to UTF-8. Because GitHub is recognizing the files that are encoded by Unicode as binary files.
* All: Added some test to confirm the behavior of Issue #18.
* NuGet: Fixed #20: Indirection stub settings for the instance method of an internal class generates build errors. => Added the judgment condition whether a method signature is public. If the method is an instance method, the type of `this` is also considered additionally.