add some iterators

* RenderWindow.events -> iterate over all the events in the events queue
* (ConvexShape - rc::ConvexShape).points -> iterate over all the points
* ConvexShape - rc::ConexShape -> trait Index
* VertexArray -> rename iter() to vertices()
clean internal sfBool -> use enum
add a drawing of VertexArray with rc::RenderStates
big code cleanup

( code style, indent, trailling whitespace, doc comments, doc comments indent)
add allow non_camel_case_type (for ffi)