Two more standard examples for type wrapping and InternalFunction

Here are two of the test files I used to get familiar with some of the concepts I needed. I've cleaned them up and commented everything.

Adding a pull request in the hopes that the next person starting on similar problems may find them useful. Feel free to commit or reject as you like.
I understand that there are old and new examples.  But let's add only new examples, so if it is not too much of a bother please use the first line of `rinside_sample15.cpp` which is what I have been using for the last few years (but what is different from what I used before that):

```c++
// -*- mode: C++; c-indent-level: 4; c-basic-offset: 4; indent-tabs-mode: nil; -*-
```