Saving pixel match info in the electron for offline ID purposes

This pull request adds the pixel seed into to the GsfElectron object to enable better electron - photon disambiguation and miss matched tracks at the identification level. This change has been agreed by E/gamma (Lindsey, Matteo,Sam) and it would be nice if we could include it into 73X
Put unsigned char after all the floats, better for byte alignment and padding in memory as far as I understand.