improved build scripts, switched from OGRE to SFML

renamed src/ to source/
renamed docs/ to doxygen/
modified README.md
modified data/CMakeLists.txt
modified source/CMakeLists.txt
removed cmake/FindOGRE.cmake
removed cmake/FindOIS.cmake
removed cmake/FindPkgMacros.cmake
removed cmake/PreprocessorUtils.cmake
removed tests/