Complete Peerunity logo integration

[Refs: Peerunity/Peerunity#42] Update all of the Peerunity icons (both realnet and testnet) and correct the locations where old Peercoin logos were being called for Windows toolbars. Remove references and assets that still called the old 'Bitcoin.png,' 'Bitcoin.ico,' and 'Bitcoin.icns' files. Remove the 'ppcoin.png,' 'ppcoin.ico,', 'ppcoin.icns,' and 'ppcoin_testnet.png' files and references.