C++interface

Created by: siebenkopf

I have implemented a C++ interface (a library and the header files) for all of our image IO functionality, and I have documented it. I have also added some tests for the new interface, which are implemented in C++ and bound to python, so that they can run in the normal nose tests. Also, I have taken care that we use the HAVE_... flags internally, so that missing libraries should not affect the build anymore.