Refactoring of src files. No serious modifs, only shape.

CMakeLists.txt

python/alpha.py

python/test_unit/eigenpy.py

python/test_unit/geometry.py

src/angle-axis.cpp

src/angle-axis.hpp

src/details.cpp

src/details.hpp

src/eigenpy.cpp

src/eigenpy.hpp

src/fwd.hpp

src/geometry.hpp

src/quaternion.cpp

src/quaternion.hpp

src/simple.cpp

src/simple.hpp

unittest/geometry.cpp

unittest/matrix.cpp