Bonding and Oxidation State of a Transition Metal Atom Encapsulated in an Isolated Octahedral Cluster Cation of Main Group Elements:  Synthesis, Crystal Structure, and Electronic Structure of Pt 2 In 14 Ga 3 O 8 F 15 Containing Highly Positive 18-Electron Complex [PtIn 6 ] 10+ and Low-Valent In + Ions