Add sgml graphics import

@cRicateau @XavierJp : *Important*

This is all that is required in the project files to get SFML to work. Everything else (path definitions...) is up to you (through your IDEs).
Make sure that you can get the program to build before merging.

@XavierJp : In xCode, I think the easiest way is to create a new SFML CLT project (requires the SFML add-on, downloadable on their website), and import all our project files. Do not forget to switch the c++ language dialect to 'c++1y' in the Build Settings.