The Binuclear Iridium(II) Hydride Complex [(C<sub>5</sub>Me<sub>5</sub>)Ir(<i>μ</i>-H)]<sub>2</sub>: A Novel Base for Reversible Deprotonation of Acidic Organic Compounds and a Unique Catalyst for C−C Bond Cleavage of Aromatic 1,2-Diols and Michael Additions