New party shared experience bonus

This closes #889.
It will return player objects and not iterator objects, so I don't think "it" is an appropriate name here. memberList also contains pointers, so using pointers instead of a reference better reflects that and removes the unnecessary reference to the pointer (if that's what is happening right now, I'm unsure). Either way, please change it to "const Player* member" to be consistent with the other loops in this class.