Removed equivalent typedefs from AbstractShape, using DimensionTraits
everywhere except for internal storage. It would possibly allow to
remove #include for specialized types from Shape headers.
Also removed Doxygen workarounds for applyTransformation(), as both the
pure virtual function and implementations have now the same signature.
Magnum.h now doesn't include anything except OpenGL headers, thus
changes in Math library don't trigger recompilation of everything, but
only of things really depending on it.
Math constants moved to separate file for similar reasons, de-inlined
some functions to remove the need for some #includes.