improved build scripts and switched from OGRE to SFML

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