Consider removing BatonHandle typedef

Currently, the baton API defines a typedef of BatonHandle for std::shared_ptr<Baton>. It's come up serveral times that it's not obvious to readers from the name that BatonHandle provides the refcounting and other particular properties of shared_ptr that are often relied on when it is used.  Since this "handle"  doesn't provide any special properties and is just a typedef, it may be worth removing the typedef and just type std::shared_ptr<Baton> to remove this ambiguity.