Add rotate method.

We have some images being uploaded where visually they are correct, but the orientation flag says they need to be rotated, messing with the auto rotate. One idea we have is to provide a way for QA to manually rotate images with complaints.

I did a lot of copying and pasting, so appreciate you looking at this.

unknowns:

* FreeImage_RotateClassic looks deprecated, but when I removed "Classic" I got errors running the tests, so I left it.
* the c method argument for angle is a double, should I make it a double here as well?
* I am not sure how to word the argument error message.
* angle degree checking in the c code is done using an fmod method, is what I have ok?