Now using std::shared_ptr instead of sfg::SharedPtr
Now using std::bind to connect methods to sfgui signals.
Now using std::dynamic_pointer_cast.

Removed no longer suppoerted sfg::DynamicPtrCast which was removed during release of C++11.
Merge branch 'sfgui-0.2-update' into dev
Some minor docu improvments.

- Added sfgui version requirement
- Added link to TinyXML2 page